WOA1 - A pivotable subrack for an electronic device - Google Patents

A pivotable subrack for an electronic device Download PDF

Info

Publication number

WOA1

WOA1 PCT/FI/ FIW WOA1 WO A1 WO A1 WO A1 FI W FI W FI W WO A1 WO A1 WO A1

Authority

WO

WIPO (PCT)

Prior art keywords

subrack

groove

edging

pivot

unit

Prior art date

-09-30

Application number

PCT/FI/

Other languages

French (fr)

Inventor

Pentti ÖSTMAN

Original Assignee

Standard Electric Puhelinteollisuus Oy

Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)

-09-30

Filing date

-09-30

Publication date

-04-07

-04-03 Priority to FIA priority Critical patent/FIC/en

-09-30 Application filed by Standard Electric Puhelinteollisuus Oy filed Critical Standard Electric Puhelinteollisuus Oy

-09-30 Priority to PCT/FI/ priority patent/WOA1/en

-04-07 Publication of WOA1 publication Critical patent/WOA1/en

Links

• Espacenet
• Global Dossier
• PatentScope
• Discuss

• edging Methods 0.000 claims abstract description 21
• coupling Effects 0.000 description 2
• coupling process Methods 0.000 description 2
• coupling reaction Methods 0.000 description 2
• Al alloy Inorganic materials 0.000 description 1
• extraction Methods 0.000 description 1
• gravity Effects 0.000 description 1
• material Substances 0.000 description 1
• transition Effects 0.000 description 1

Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K7/00—Constructional details common to different types of electric apparatus
  • H05K7/14—Mounting supporting structure in casing or on frame or rack
  • H05K7/16—Mounting supporting structure in casing or on frame or rack on hinges or pivots

Definitions

• the invention relates to a subrack to be mounted within a cabinet, a rack or the like housing as a structurally independent unit of an electronic device or the like, which subrack forms the primary structure for component boards, plug-in units and other components of the device and which is removable from within the housing and pivotable on an edging provided on the back edge of a lower rail of the subrack in such a manner that a back face of the subrack becomes accessible.
• Pivotable industrially utilized structures are usually so constructed that the subrack is secured on a pivoted frame which has the shape of a right-angled parallelogram and which is positioned within a cabinet or the like housing and hinged e.g. on the wall of the housing at one vertical side thereof.
• the subrack is pivoted with this hinged, pivoted frame.
• Another used structure comprises slide bars or the like which have a telescopic structure and which are fastened on the side plates of the subrack and by means of which the subrack is first extracted sufficiently from within the housing and thereafter pivoted in front of the housing, whereby the pivot shafts are positioned at the ends of the telescopic bars.
• the object of the present invention is to eliminate the above disadvantages and provide a pivotable subrack structure which is suited for various purposes.
• the invention is characterized by the features disclosed in the attached claims.
• the subrack which is formed as a structurally independent unit, is pivoted on a shaft point, i.e. a pivot joint which is formed by the compo ⁇ nents of the subrack unit itself.
• the upper and the lower rails of the subrack unit according to the inven ⁇ tion differ in shape from the conventional ones.
• the front edge of the upper rail is provided with a groove or the like extending in the direction of the length of the rail and intended for the pivoting and supporting of the subrack.
• the back edge of the lower rail of the subrack unit is provided with an edging which fits said groove.
• the groove and the edging together form the pivot joint when two subrack units according to the invention are psoitioned one upon the other within a cabinet or the like housing, and the upper one is loosened and drawn out until the edging of the lower rail thereof falls into the groove of the upper rail of the subrack unit beneath.
• Figure 1 is a front view of subrack units accord ⁇ ing to the invention when these are fastened within a cabinet or the like housing,
• Figure 2 is a side view of the subrack units of Figure 1 within a cabinet as a section along the line II-II of Figure 1 ,
• Figure 3 is a top view of the subrack units of Figure 1 within a cabinet as a section along the line III-III of Figure 1
• Figure 4 illustrates the subrack units of Figure 3 in a situation wherein the upper ' subrack has been loosened from the cabinet and drawn out so that the pivot edging of the lower rail thereof has slid into the pivot groove of the upper rail of the lower subrack unit
• Figure 5 illustrates the subrack units of Figure 4 in a position in which the upper subrack unit has been pivoted in front of the cabinet on the pivot joint and supported by the joint in a position which allows the back face of the subrack unit to be reached
• Figure 6 is a partial enlarged view of the pivot joint of Figure 5.
• Figure 1 shows two subrack units according to the invention positioned within a cabinet.
• the frame of the subrack unit is here formed by an upper rail 1 , a lower rail 2 and two side plates 3. Further, a front panel 6 of a component board 5 positioned within the subrack unit is also illustrated in the figure 1.
• the subrack units are fastened by means of screws 7 in the cabinet in such a manner that a suitable clearance is provided between them and the cover and the base of the cabinet as shown e.g. in Figure- 2.
• Figure 2 shows the cabinet of Figure 1 as a section along the line II-II of Figure 1.
• a groove 11 is provided on the upper surface of the upper rail 1 close to the front face of the cabinet, the cross-section of the groove having substantially the shape of a paralle ⁇ logram the vertical sides of which are at an angle of about 45°, for instance, with the side forming the bottom of the groove.
• the groove opens obliquely upwards on the front side of the cabinet.
• the back edge of the lower rail 2 is provided with a downwardly projecting listlike edging 12, whereby that corner of the edging which is positioned on the front side of the cabinet is rounded.
• the groove 11 and the edging 12 together form a pivot joint, as will be more closely described in connection with Figures.4, 5 and 6.
• Figure 2 further shows a component board 5 which is illustrated by means of diagonal lines drawn on the surface thereof from one corner to another. Additionally, Figure 2 shows a back plate 4 or the like which is fastened on the subrack unit and whereto connectors and cables 8 brought to the subrack unit are attached.
• Figure 3 illustrates the cabinet of Figure 1 as a section along the line III-III of Figure 1.
• the upper rail 1 is provided with a pivot groove 11 extending in the longitudinal direction of the rail. That edge of the pivot groove which is positioned on the front side thereof forms a slightly elevated threshold 13 ( Figure 6) which prevents the pivot edging 12 of the lower rail 2 of the subrack unit from sliding over the pivot groove 11 of the upper rail 1 at the extraction stage of Fig ⁇ ure 4.
• the height of the threshold is about half of the vertical clearance. It further appears from Figure 3 that the cables 8 brought to the back face of the subrack unit can be attached thereto over the entire width of the back plate 4 without difficulty.
• Figures 5 and 6 illustrate the pivoting of an extracted subrack unit on a joint formed by the pivot groove 11 and the pivot edging 12.
• the edging 12 can be easily passed into the groove 11, and the subrack can be tilted substantially to such an extent as is allowed by the inclination of groove 11.
• the back face of the edging 12 and the back face of the groove 11 are thereby positioned against each other, thus preventing further tilting of the subrack unit.
• the subrack does not require any further supportion in order to be maintained in the tilted position shown in Figure 5.
• the angle of inclination of the subrack unit is indicated by the reference C , and this angle may vary e.g. 40 or more; however, if two subracks positioned one upon the other are to be drawn out -simultaneousl , the angle oC should be 45 or less in order to ensure that the upper subrack will be maintained in position on the pivot joint thereof.
• Figures 4 and 5 illustrate the pivoting of the upper subrack only. It is also possible to pivot the lower subrack and, if desired,, the lower subrack together with the upper subrack, as already mentioned above, when a separate upper rail 1 is fastened on the base of the cabinet. This rail 1 is shown in Figure 2, 4 and 5.
• this loosely pivotable subrack unit according to the invention provides an advantage in that no separate pivoted frames or telescopic structures are necessary. Consequently, no additional room is required by the pivotable subrack according to the invention in the cabinet. Furthermore, ' the cables can be led easily within the housing on the sides of the subrack since the structure is open and there are no hampering bars or hinges. If required, the subrack unit according to the invention can be lifted off the joint 11, 12 out of the cabinet with the cables coupled. -
• the different embodiments of the invention may vary within the scope of the claims. So it is not essential of what size the subrack units are and how the details of the components thereof are dimensioned. ' It is essential that the upper and the lower rail of the subrack units can be fitted together so that they form a joint extending in the direction of the width of the subrack unit, and that the position and the shape of the joint are such that the subrack unit can be tilted by means thereof and supported in such a position in front of the housing that the centre of gravity of the subrack unit is outside the housing, whereby the back face of the subrack is easily accessible.

Landscapes

• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Casings For Electric Apparatus (AREA)

Abstract

Subrack to be mounted within a cabinet, a rack or the like housing in an electronic device or the like, which subrack forms the supporting structure for component boards (5), plug-in units and the other components of the device and which can be removed from within the housing and pivoted in such a manner that the back face of the subrack becomes accessible. This pivoting possibility has been achieved by means of a simple structure which requires less room in such a manner that the subrack, which is formed as a structurally independent unit, is provided at the front edge of the upper rail (1) thereof with a groove or the like extending in the direction of the length of the rail and on the back edge of the lower rail (2) thereof with an edging which is adapted to pivot on said groove.

Description

A pivotable subrack for an electronic device The invention relates to a subrack to be mounted within a cabinet, a rack or the like housing as a structurally independent unit of an electronic device or the like, which subrack forms the primary structure for component boards, plug-in units and other components of the device and which is removable from within the housing and pivotable on an edging provided on the back edge of a lower rail of the subrack in such a manner that a back face of the subrack becomes accessible. Pivotable industrially utilized structures are usually so constructed that the subrack is secured on a pivoted frame which has the shape of a right-angled parallelogram and which is positioned within a cabinet or the like housing and hinged e.g. on the wall of the housing at one vertical side thereof. The subrack is pivoted with this hinged, pivoted frame. Another used structure comprises slide bars or the like which have a telescopic structure and which are fastened on the side plates of the subrack and by means of which the subrack is first extracted sufficiently from within the housing and thereafter pivoted in front of the housing, whereby the pivot shafts are positioned at the ends of the telescopic bars. This kind of pivoted frames and telescopic struc¬ tures, however, are disadvantageous in many respects. The structures are expensive, and the fastening thereof both on the housing and the subrack requires several compo-' nents and several finishing steps. They take plenty of room on the sides of the subrack, and thereby increase the width as well as the other dimensions of the cabinet or the like housing. In addition, pivoted frames and telescopic structures secured between the subrack and its housing hamper the passage of cables led to the the subrack and reduce coupling possibilities. The object of the present invention is to eliminate the above disadvantages and provide a pivotable subrack structure which is suited for various purposes. The invention is characterized by the features disclosed in the attached claims. The subrack, which is formed as a structurally independent unit, is pivoted on a shaft point, i.e. a pivot joint which is formed by the compo¬ nents of the subrack unit itself. The upper and the lower rails of the subrack unit according to the inven¬ tion differ in shape from the conventional ones. The front edge of the upper rail is provided with a groove or the like extending in the direction of the length of the rail and intended for the pivoting and supporting of the subrack. Correspondingly, the back edge of the lower rail of the subrack unit is provided with an edging which fits said groove. The groove and the edging together form the pivot joint when two subrack units according to the invention are psoitioned one upon the other within a cabinet or the like housing, and the upper one is loosened and drawn out until the edging of the lower rail thereof falls into the groove of the upper rail of the subrack unit beneath. The invention will be described in detail with reference to the attached drawings, wherein Figure 1 is a front view of subrack units accord¬ ing to the invention when these are fastened within a cabinet or the like housing, Figure 2 is a side view of the subrack units of Figure 1 within a cabinet as a section along the line II-II of Figure 1 , Figure 3 is a top view of the subrack units of Figure 1 within a cabinet as a section along the line III-III of Figure 1 , Figure 4 illustrates the subrack units of Figure 3 in a situation wherein the upper' subrack has been loosened from the cabinet and drawn out so that the pivot edging of the lower rail thereof has slid into the pivot groove of the upper rail of the lower subrack unit, Figure 5 illustrates the subrack units of Figure 4 in a position in which the upper subrack unit has been pivoted in front of the cabinet on the pivot joint and supported by the joint in a position which allows the back face of the subrack unit to be reached, and Figure 6 is a partial enlarged view of the pivot joint of Figure 5. Figure 1 shows two subrack units according to the invention positioned within a cabinet. The frame of the subrack unit is here formed by an upper rail 1 , a lower rail 2 and two side plates 3. Further, a front panel 6 of a component board 5 positioned within the subrack unit is also illustrated in the figure 1. The subrack units are fastened by means of screws 7 in the cabinet in such a manner that a suitable clearance is provided between them and the cover and the base of the cabinet as shown e.g. in Figure- 2. Figure 2 shows the cabinet of Figure 1 as a section along the line II-II of Figure 1. As appears from Figure 2 and in more detail from Figure 6, a groove 11 is provided on the upper surface of the upper rail 1 close to the front face of the cabinet, the cross-section of the groove having substantially the shape of a paralle¬ logram the vertical sides of which are at an angle of about 45°, for instance, with the side forming the bottom of the groove. Thus the groove opens obliquely upwards on the front side of the cabinet. The back edge of the lower rail 2, in turn, is provided with a downwardly projecting listlike edging 12, whereby that corner of the edging which is positioned on the front side of the cabinet is rounded. The groove 11 and the edging 12 together form a pivot joint, as will be more closely described in connection with Figures.4, 5 and 6. Figure 2 further shows a component board 5 which is illustrated by means of diagonal lines drawn on the surface thereof from one corner to another. Additionally, Figure 2 shows a back plate 4 or the like which is fastened on the subrack unit and whereto connectors and cables 8 brought to the subrack unit are attached. Figure 3 illustrates the cabinet of Figure 1 as a section along the line III-III of Figure 1. The upper rail 1 is provided with a pivot groove 11 extending in the longitudinal direction of the rail. That edge of the pivot groove which is positioned on the front side thereof forms a slightly elevated threshold 13 (Figure 6) which prevents the pivot edging 12 of the lower rail 2 of the subrack unit from sliding over the pivot groove 11 of the upper rail 1 at the extraction stage of Fig¬ ure 4. The height of the threshold is about half of the vertical clearance. It further appears from Figure 3 that the cables 8 brought to the back face of the subrack unit can be attached thereto over the entire width of the back plate 4 without difficulty. In figure 4, the fastening screws 7 of the upper subrack unit have been loosened so that the subrack unit has fallen downwards a distance corresponding to the clearence, and the lower rail 2 is supported on the lower subrack unit. The subrack unit has been drawn horizontally outwards until the pivot edging 12 of the lower rail 2 has slid into the pivot groove 11 on the upper rail 1 of the lower subrack unit. The patch C-C of the subrack unit is indicated by a dot-and-dash line in the figure. Figures 5 and 6 illustrate the pivoting of an extracted subrack unit on a joint formed by the pivot groove 11 and the pivot edging 12. By virtue of the inclined position of the groove 11 and the rounding of the front corner of the edging 12, the edging 12 can be easily passed into the groove 11, and the subrack can be tilted substantially to such an extent as is allowed by the inclination of groove 11. The back face of the edging 12 and the back face of the groove 11 are thereby positioned against each other, thus preventing further tilting of the subrack unit. When the upper and the lower rails 1 and 2 and the grooves 11 and the edgings 12 thereof are manufactured of a sufficiently strong material, such as e.g. an aluminium alloy, the subrack does not require any further supportion in order to be maintained in the tilted position shown in Figure 5. The angle of inclination of the subrack unit is indicated by the reference C , and this angle may vary e.g. 40 or more; however, if two subracks positioned one upon the other are to be drawn out -simultaneousl , the angle oC should be 45 or less in order to ensure that the upper subrack will be maintained in position on the pivot joint thereof. When the subrack has been tilted backwards, its back face, the back plate 4 and the cables 8 are easily accessible through the formed opening. The path of the backmost upper corner of the subrack is indicated by the broken line C-C'-C11. Figures 4 and 5 illustrate the pivoting of the upper subrack only. It is also possible to pivot the lower subrack and, if desired,, the lower subrack together with the upper subrack, as already mentioned above, when a separate upper rail 1 is fastened on the base of the cabinet. This rail 1 is shown in Figure 2, 4 and 5. In comparison with prior solutions, this loosely pivotable subrack unit according to the invention provides an advantage in that no separate pivoted frames or telescopic structures are necessary. Consequently, no additional room is required by the pivotable subrack according to the invention in the cabinet. Furthermore, 'the cables can be led easily within the housing on the sides of the subrack since the structure is open and there are no hampering bars or hinges. If required, the subrack unit according to the invention can be lifted off the joint 11, 12 out of the cabinet with the cables coupled. - As the pivot edging 12 provided on the lower rail 12 of the subrack unit is horizontally positioned, a f rther advantage is obtained in' that the cables to be installed at the the back of the subrack unit can be attached thereto over the entire width of the subrack unit, and at the same time the length and the transition of the cables are at their minimum, and in that even with an angle of inclination (σ ) of 45 the back portion of a subrack is sufficiently visible for the reparations and couplings to be carried out without difficulty* The different embodiments of the invention may vary within the scope of the claims. So it is not essential of what size the subrack units are and how the details of the components thereof are dimensioned.' It is essential that the upper and the lower rail of the subrack units can be fitted together so that they form a joint extending in the direction of the width of the subrack unit, and that the position and the shape of the joint are such that the subrack unit can be tilted by means thereof and supported in such a position in front of the housing that the centre of gravity of the subrack unit is outside the housing, whereby the back face of the subrack is easily accessible.

Claims

Claims: 1. A subrack to be mounted within a cabinet, a rack or the like housing as a structurally independent unit of an electronic device or the like, which subrack forms a primary structure for component boards (5) , plug-in unit's and other components of the device and which is removable from within the housing and pivotable on an edging (12) provided on the back edge of a lower rail (2) of the subrack in such a manner that a back face (4) of the subrack becomes accessible, c h a r a c t e r i z e d in that a groove (11) or the like extending in the direction of the length of the upper rail (1) of the subrack is provided on said rail (1) close to the forward edge thereof, the edging (12) of the back edge of the lower rail being adapted to pivot on said groove (11) . 2. A subrack according to claim 1 , c h a r a c t e r i z e d in that the edging (12) and the groove (11) forming the pivot joint are adapted to interact so as to define the maximum pivot angle (oC) of the subrack unit, whereby the height of the edging (12) forms the torgue arm between the supporting points which restrict the pivot movement. 3. A subrack according to claim 1 or 2, c h a r a c t e r i z e d in that the edge of the upper rail (1) on the front side of the pivot groove (11) forms a slightly elevated treshold (13) . PCT/FI/ -04-03 -09-30 A pivotable subrack for an electronic device WOA1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title FIA FIC (en) -04-03 -04-03 Reversible frame for an electronic device PCT/FI/ WOA1 (en) -09-30 -09-30 A pivotable subrack for an electronic device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title PCT/FI/ WOA1 (en) -09-30 -09-30 A pivotable subrack for an electronic device

Publications (1)

Publication Number Publication Date WOA1 true WOA1 (en) -04-07

Family

ID=

Family Applications (1)

Application Number Title Priority Date Filing Date PCT/FI/ WOA1 (en) -04-03 -09-30 A pivotable subrack for an electronic device

Country Status (1)

Country Link WO (1) WOA1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title DEA1 (en) * -11-26 -05-31 Festo Kg POWER SUPPLY UNIT WOA1 (en) * -06-13 -12-23 Elin Energieversorgung Gesellschaft M.B.H. Housing for plug-in packages of electronic components DEU1 (en) * -10-31 -12-21 GEN Computer Systeme GmbH, Neuss Computer case GBA (en) * -01-29 -08-05 Beckman Wysse Limited Equipment rack with retractable cable management system USB1 (en) -03-13 -02-23 Anthony Eugene Forney Responsive support system and mount

Citations (9)

* Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title USA (en) * -04-24 -10-13 Grant Pulley & Hardware Corp Pivotally movable sliding bracket for drawers or shelves and locking means therefor USA (en) * -03-01 -10-08 Fall Herbert Scott Electronic assembly chassis supporting track USA (en) * -01-31 -10-14 Stewart Warner Corp Cabinet installed electronic apparatus USA (en) * -11-28 -01-20 Hough John Jay Mechanism for mounting electrical units USA (en) * -07-27 -08-25 Sylvania Electric Prod Cabinet for electronic equipment USA (en) * -11-02 -03-31 Digital Equipment Corporation Integral pivot and lock apparatus for slide rack mounted boxes USA (en) * -05-07 -02-09 Sybron Corporation Cabinet drawer support SEB (en) * -08-05 -02-21 Eldon Ab Method and arrangement for installation of a component rack provided with components in an instrument cabinet USA (en) * -02-08 -04-10 Roesler Layton S Drawer apparatus

• • -09-30 WO PCT/FI/ patent/WOA1/en unknown

Patent Citations (9)

* Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title USA (en) * -04-24 -10-13 Grant Pulley & Hardware Corp Pivotally movable sliding bracket for drawers or shelves and locking means therefor USA (en) * -01-31 -10-14 Stewart Warner Corp Cabinet installed electronic apparatus USA (en) * -03-01 -10-08 Fall Herbert Scott Electronic assembly chassis supporting track USA (en) * -11-28 -01-20 Hough John Jay Mechanism for mounting electrical units USA (en) * -07-27 -08-25 Sylvania Electric Prod Cabinet for electronic equipment USA (en) * -11-02 -03-31 Digital Equipment Corporation Integral pivot and lock apparatus for slide rack mounted boxes USA (en) * -05-07 -02-09 Sybron Corporation Cabinet drawer support SEB (en) * -08-05 -02-21 Eldon Ab Method and arrangement for installation of a component rack provided with components in an instrument cabinet USA (en) * -02-08 -04-10 Roesler Layton S Drawer apparatus

Cited By (7)

* Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title DEA1 (en) * -11-26 -05-31 Festo Kg POWER SUPPLY UNIT WOA1 (en) * -06-13 -12-23 Elin Energieversorgung Gesellschaft M.B.H. Housing for plug-in packages of electronic components ATB (en) * -06-13 -06-26 Elin Energieversorgung HOUSING FOR INSERTS OF ELECTRONIC ASSEMBLIES DEU1 (en) * -10-31 -12-21 GEN Computer Systeme GmbH, Neuss Computer case GBA (en) * -01-29 -08-05 Beckman Wysse Limited Equipment rack with retractable cable management system GBB (en) * -01-29 -09-29 Beckman Wysse Limited Equipment rack USB1 (en) -03-13 -02-23 Anthony Eugene Forney Responsive support system and mount

Similar Documents

Publication Publication Date Title USA (en) -02-01 Computer and a rack mount system and method for a computer USA (en) -08-14 Desk with concealed wire storage USA (en) -02-13 Aligned quick connect cover for a computer system EPB1 (en) -07-17 Adjustable monitor support assembly USA (en) -10-28 Computer work station EPB1 (en) -02-22 Improvements in or relating to enclosures USB1 (en) -02-27 Tiltable electronics cabinet USB1 (en) -01-16 Equipment arrangement CAC (en) -07-09 Hinged brackets WOA1 (en) -04-07 A pivotable subrack for an electronic device CAC (en) -05-19 Sliding door fitting RUA (en) -12-27 LOCATION OF EQUIPMENT USA1 (en) -07-11 Control console EPA3 (en) -01-20 Simplified universal drawer guiding system CAC (en) -02-12 Control console CNU (en) -02-05 Drawer and cabinet comprising same GBA (en) -07-26 Top and base assembly USA (en) -07-30 Sliding ice rink door USA (en) -02-25 Protective cover for electrical assembly unit USA (en) -03-19 Electrical apparatus frame EPB1 (en) -04-09 A shelf ATET1 (en) -06-15 DOOR FOR WALL MOUNTED FURNITURE. FIB (en) -09-29 VAENDBAR RAM FOER EN ELEKTRONIKANORDNING. JPB2 (en) -07-11 Storage JPHA (en) -07-22 Cooling structure for electronic apparatus

Legal Events

Date Code Title Description

FAQ on VME history and basic technology

Portions of this FAQ have been reprinted (with permission) from The VMEbus Handbook, 4th Edition by Wade D. Peterson, VITA . For more details the user is directed to the handbook, or the VMEbus specification(s). Other items have been reprinted from the VITA Journal (with permission) VMEbus FAQ's article series by John Rynearson.

Rdekono contains other products and information you need, so please check it out.

• Why was VMEbus created in the first place?
• What are the general VMEbus features?
• What is VMEbus used for?
• What was the 'original' VMEbus standard?
• What's the difference between VMEbus and VME64?
• What are the VME64 extensions (VME64x)?
• What is VME320 (and or the 2eSST protocol)?
• What software runs on VMEbus computers?
• How fast is VMEbus?
• How does it work?
• What are address modifier codes?
• What are the various address and data size capabilities?
• What are the bus grant and interrupt acknowledge chains?
• Can it support multiple bus masters (arbitration)?
• What is the slot 1 system controller?
• What is metastability? Why is it important to VMEbus board designers?
• What type of mechanical hardware does VMEbus use?
• What styles of backplanes are available?
• What if I need more than 21 slots in a backplane (i.e. multi-crate operation)?
• Can I get conduction cooled hardware?
• What's the difference between the 96-pin and 160-pin connectors?
• Are the two styles of connectors compatible?
• What is the 'P0/J0' connector?
• What are the P2/J2 user defined pins?
• What is a mezzanine module?
• What is the VSB, the VMEbus Subsystem Bus?
• What is live insertion (hot swap)?
• What is SCSA (relating to telephony applications)?
• Where can I get a copy of the VMEbus specification?
• Who makes VMEbus equipment?
• Is there a forum for VMEbus users?
• Are there any VMEbus application notes available?

Introduction to VMEbus

VMEbus is a computer architecture. The term 'VME' stands for VERSAmodule Eurocard and was first coined in by the group of manufacturers who defined it. This group was composed of people from Motorola, Mostek and Signetics corporations who were cooperating to define the standard. The term 'bus' is a generic term describing a computer data path, hence the name VMEbus.

Actually, the origin of the term 'VME' has never been formally defined. Other widely used definitions are VERSAbus-E, VERSAmodule Europe and VERSAmodule European. However, the term 'Eurocard' tends to fit better, as VMEbus was originally a combination of the VERSAbus electrical standard, and the Eurocard mechanical form factor.

VERSAbus was first defined by Motorola Corporation in for its microprocessor. Initially, it competed with other buses such as Multibus™, STD Bus, S-100 and Q-bus. However, it is rarely used anymore.

The microcomputer bus industry began with the advent of the microprocessor, and in many buses were showing their age. Most worked well with only one or two types of microprocessors, had a small addressing range and were rather slow. The VMEbus architects were charged with defining a new bus that would be microprocessor independent, easily upgraded from 16 to 32-bit data paths, implement a reliable mechanical standard and allow independent vendors to build compatible products. No proprietary rights were assigned to the new bus, which helped stimulate third party product development. Anyone can make VMEbus products without any royalty fees or licenses.

Since much work was already done on VERSAbus it was used as a framework for the new standard. In addition, a mechanical standard based on the Eurocard format was chosen. Eurocard is a term which loosely describes a family of products based around the DIN and IEC 603-2 connector standards, the IEEE PC board standards and the DIN and IEC 297-3 rack standards. When VMEbus was first developed, the Eurocard format had been well established in Europe for several years. A large body of mechanical hardware such as card cages, connectors and sub-racks were readily available. The pin and socket connector scheme is more resilient to mechanical wear than older printed circuit board edge connectors.

The marriage of the VERSAbus electrical specification and the Eurocard format resulted in VMEbus Revision A. It was released in .

The VMEbus specification has since been refined through revisions B, C, C.1, IEC 821, IEEE - and ANSI/VITA 1-. The ANSI, VITA, IEC and IEEE standards are important because they make VMEbus a publicly defined specification. Since no proprietary rights are assigned to it, vendors and users need not worry that their products will become obsolete at the whim of any single manufacturer.

Since its introduction, VMEbus has generated thousands of products and attracted hundreds of manufacturers of boards, mechanical hardware, software and bus interface chips. It continues to grow and support diverse applications such as industrial controls, military, telecommunications, office automation and instrumentation systems.

Why VMEbus Was Created in the First Place

There were several reasons why VMEbus was created in the first place. To understand these, we must first look back to the computer industry in about . At that time if you wanted to buy a computer, then you had to shop at a short list of companies that included Control Data, Cray Research, Data General, Digital Equipment, IBM, Sperry-Univac and a few others. These companies made big, bulky and expensive computers called mainframes and minicomputers.

In the late 's a new class of machine called the desktop computer (or personal computer) emerged. These were powered by small, low cost microprocessors that dramatically cut the size and price of the computer. They became immensely popular, and companies began to experiment with them in industrial control systems. They found that desktop computers worked great in those applications, but had two major drawbacks...they weren't durable enough and they couldn't be modified very easily. Both were severe problems for the embedded control systems of the time.

This was the situation in when the VMEbus architecture was born. The new design combined the VERSAbus electrical specification, which was based on microprocessor technology, with the rugged and modular Eurocard packaging system. Both were proven, off-the-shelf technologies. The resulting combination was successful because it solved the durability problem and could be easily adapted to a wide variety of applications. However, this was only part of the story, as there was also a business strategy behind VMEbus that solved some very difficult market problems.

By the time VMEbus arrived in , the computer industry was maturing, and suffered from a lack of competitiveness. While buyers could choose equipment and software from among a small group of manufacturers, there really wasn't much competition. There were a variety of reasons for this, but a big one was the lack of technical standards. For example, if you designed an accounting system around the IBM 360, then you wouldn't be able to move it over to a Digital Equipment Corporation VAX...at least not without spending a lot of time and money. IBM 360's just didn't connect to VAXes very well, and the software wasn't very transportable from one to another either.

This situation was very good for the computer companies of the day because it allowed each one to dominate a market niche. It was a sellers market where direct competition was squashed because there were few open technical standards. It was also bad for consumers (i.e. the system integrators) who had to pay higher prices for equipment and software. They also had fewer choices because it was very difficult for third parties to enter the market with their own innovative ideas.

VMEbus was done a little differently. The original planners had the foresight to place the VMEbus specification into the public domain. This not only meant that everybody had to conform to the same technical standard, it also meant that they had to compete directly on the basis of price, performance, quality and time-to-market. It was a buyers market that meant lower margins for the suppliers, but also lower costs for the consumer ( i.e. the ones with the money). The adoption of VMEbus as a public domain standard was a shrewd political move because it was easier to accept by a group of competitors. The new market also had low barriers to entry which meant that third parties could enter the marketplace more easily.

In the beginning, many predicted that this new, open marketplace was doomed to failure. There were many sound business reasons for this at the time, but eventually it succeeded. That's because the system integrators...or at least those paying for the system integration...liked the buyer's market better. Ironically, it was also good for the suppliers because the lower prices increased the demand for their products. They made lower margins, but made up for that with higher volumes.

General VMEbus Features

Table 1 shows the general VMEbus features under the VME64 and VME64x specifications. A variety of other 'accessory' standards are also available with VMEbus products, but may not be mentioned in this FAQ. These include (but are not limited to) mezzanine modules, crossbar switches, serial channels and high-availability type products.

VMEbus Applications

VMEbus is used in a wide variety of applications. In many cases, the VMEbus system design has been tailored to support specialized applications as well. Some of the most popular include:

• Industrial controls: factory automation, robotics, injection molding machines, automotive body assembly and painting, sawmill controls, metal working, steel manufacturing, cardboard cutters and many others.
• Military: battlefield command & control systems, ground and flight radar control systems, tank and gun controls, communications, avionics and many others.
• Aerospace: avionics, fly-by-wire control systems, in-flight video servers, spacecraft experiment control, missile countdown sequencers, and many others. In the Mars Pathfinder used a VMEbus computer to control spacecraft operation on the planet Mars.
• Transportation: railway controls, smart highway systems and light-rail transit systems.
• Telecom: advanced intelligent node (AIN) switch gear, cellular base stations, satellite uplink and downlinks and switches. VMEbus live insertion capabilities were also designed for this application.
• Simulation: aircraft flight, earthquake, metal fatigue and various military simulation systems.
• Medical: CATSCAN imaging, MRI imaging and various acoustical systems.
• High Energy Physics: particle accelerators, particle detectors.
• General business: network routers, servers, copy machines and high-speed printers.

Original VMEbus (IEEE--)

The original VMEbus specification (IEEE--) has a robust set of features. These are just a subset of the current VMEbus offerings, but included:

• MASTER/SLAVE architecture.
• Asynchronous bus (no clocks are used to coordinate data transfers).
• Variable speed handshaking protocol.
• Non-multiplexed bus.
• Addressing range between 16 and 32-bits.
• Data path widths of between 8 and 32-bits.
• Bandwidths up to 40 Mbyte/second.
• Multiprocessing capability.
• Interrupt capability.
• Wide variety of mechanical hardware based on the IEEE standard.
• Up to 21 card slots can be used in a single backplane.

Noteworthy functions include (up to) 32-bit address and data buses, multiprocessing capability and seven level interrupt protocol. Both the address and data buses can be dynamically configured (i.e. they change widths automatically). This allows system expansion as microcomputer technology grows. It also handles data transfer speeds to 40 Mbytes/second.

VMEbus uses a master-slave architecture. Functional modules called masters transfer data to and from functional modules called slaves. Since many masters can reside on the bus it is called a multiprocessing bus. Before a master can transfer data it must first acquire the bus using a central arbiter. This arbiter is part of a module called the system controller. Its function is to determine which master gets access to the bus. All bus activity takes place on five sub-buses. These are called the Data Transfer Bus, the Data Transfer Arbitration Bus, the Priority Interrupt Bus, the Utility bus and the Serial Bus.

VMEbus is an asynchronous bus. That means that there are no clocks used coordinate data transfers. Data is passed between modules using interlocked handshaking signals. The cycle speed of each transfer is set by the slowest module participating in the cycle.

The maximum speed of asynchronous buses is limited by the propagation delay of signals across backplanes and through buffer ICs. A VMEbus backplane can be up to 500 mm (19.68") in length and can have relatively high inductive and capacitive loads on the signal traces. If VMEbus were synchronous, it would probably have a system clock speed of around 10 MHz. This allows about 100 nanoseconds for a signal to propagate from a master at one end of a bus, through the backplane and interface ICs, and then back again.

As we'll see shortly, the basic capabilities of VMEbus have been greatly expanded since its inception. These enhancements have taken the form of VME64, VME64x and VME320 technologies.

VME64

The most recent version of VMEbus is the ANSI/VITA 1-, which is also known as VME64. Since its approval in , a variety of boards and chips have been introduced to support the new standard. As the next generation architecture for VMEbus, VME64 promises to extend the life of VMEbus well into the 21st century. The new standard offers a much-needed 'face-lift', with enhancements such as higher bandwidths, larger address spaces and easier-to-use cards.

VME64 is a mechanical and electrical 'superset' of the original IEEE - standard. It offers new features such as:

• Larger, 64-bit data path for 6U boards.
• Larger, 64-bit addressing range for 6U boards.
• 32-bit data and 40-bit addressing modes for 3U boards.
• Twice the bandwidth (up to 80 Mbytes/sec).
• Lower noise connector system.
• Cycle retry capability.
• Bus LOCK cycles.
• First slot detector.
• Automatic 'plug-and-play' features.
• Configuration ROM / CSR capability.
• Re-definition of SERCLK and SERDAT pins.

Actually, the term 'VME64' is something of a misnomer, as all VMEbus modules that conform to the IEEE-- are now considered to be VME64 compliant (regardless of their data transfer capability). For example, a 16 or 32-bit CPU board designed under the older specification can be (correctly) identified as VME64 compatible.

All of the enhancements under VME64 and VME64x are optional. New products work in conjunction with older 'legacy' boards, thereby providing a smooth upgrade path for system integrators.

The VME64 Extensions (VME64x)

In the VITA Standards Organization (VSO) adopted a superset to the VME64 standard. The new standard is called the VME64 Extensions (VME64x). VME64x adds new capabilities such as:

• A new 160 pin connector family.
• A 95 pin P0/J0 connector.
• 3.3 V power supply pins.
• More +5 VDC power supply pins.
• Geographical addressing.
• Higher bandwidth bus cycles (up to 160 Mbytes/sec).
• 141 more user-defined I/O pins.
• Rear plug-in units (transition modules).
• Live insertion / hot-swap capability.
• Injector / ejector locking handles.
• EMC (ElectroMagnetic Compatible) front panels.
• ESD (Electrostatic Discharge) features.

The VME64x standard also lays the groundwork for the High Availability and Live Insertion (Hot Swap) VME64x standards. These are emerging standards, and will not be covered in great detail in this FAQ.

All legacy VME and VME64 modules are forward compatible to VME64x backplanes and sub-racks. That means that older bus modules can be plugged into newer systems.

In general, the reverse is also true. Bus modules designed to the VME64x standard are also backward compatible with older backplanes and subracks. For example, the new 160 pin connectors can be plugged into an older backplane. However, there are a few exceptions to this. For example, if a board requires the new +3.3 VDC power supplies, then it will not work in an older backplane (which does not have these power pins).

The VME64x standard describes many optional features. However, the standard insists that a minimum set of features be present on boards and backplanes before they are considered to be VME64x compliant. All of the other features in the standard are considered optional. For example, the minimum features that must be present on 6U modules include:

• 160 pin connectors.
• All defined grounds must be connected (row 'd' is optional).

The minimum features that must be present on a 6U backplane include:

• 160 pin connectors.
• All defined grounds must be connected.
• Monolithic PCB (i.e. must include both J1 and J2 connectors).
• Geographical address pins.
• Must route and terminate all VME64 and VME64x bused signal lines.
• Power connection and distribution for +5V, +3.3V, +/- 12V, +/- V1, +/- V2 and VPC.
• If rear (user defined) I/O pins are supported, then the rear connections must comply with the IEEE 101.11 rear I/O transition board standard.

VME320

In a modified VMEbus architecture called VME320 was released by Arizona Digital, Inc. The VME320 architecture was designed for operation at over 320 Mbyte/second, and peak bandwidths of over 500 Mbyte/second. VME320 uses a new backplane design and bus protocol. It is a proprietary architecture, and the inventors claim to have patent protection on the backplane technology within the United States of America. However, VMEbus modules can be designed, built and sold without license.

The VME320 backplane uses a 'star' interconnection method to speed up the VMEbus backplane itself. All of the interconnections on the backplane are connected together at the middle slot of the backplane. In a nutshell, the idea behind this backplane is that the leading edges of signals, propagating from slot-to-slot, will effectively pass through only one slot on the way to their destination. This allows tighter skew delays on the backplane, thereby speeding up the system.

The VME320 concept uses a new bus protocol called 2eSST. The protocol allows VME320 compatible modules to interact at much higher speeds.

VMEbus Software

VMEbus has the largest software base of any computer architecture. That's quite a claim, but it is supported by the fact that there are over 103 known, commercial operating systems running on VMEbus. Other, proprietary operating systems are also known to exist. Table 2 shows just a few examples.

VMEbus Data Transfer Speeds

VMEbus is quite fast, especially in it's most recent manifestations. In fact, it is arguably the fastest of all of the popular microcomputer buses, and certainly the fastest among the 'big commercial backplane buses' (i.e. > 8 slots). Table 3 shows the typical, maximum data transfer speeds that can be achieved between VMEbus modules. The actual data transfer rate of a VMEbus module may be slower than that shown in the Table. The user is advised to contact the board manufacturer for more details.

For further information about the speed of VMEbus, click here.

The VMEbus Architecture

For the purposes of this FAQ, we'll describe the VMEbus architecture from the standpoint of the VME64 and VME64x standards. Furthermore, we'll use the nomenclature that's used in the standard(s).

The VMEbus architecture is generally described using a concept of functional modules. These functional modules are a conceptual tool. However, in some cases they also describe actual hardware. Table 4 describes all of the functional modules available on VMEbus.

For more Subrack Chassisinformation, please contact us. We will provide professional answers.

Featured content:
Questions You Should Know about Plate Frame Filter
5 Must-Have Features in a silver plating machine

The various functional modules communicate with each other over the five sub-buses shown in Table 5. The sub-buses are also a conceptual tool, and are often used in conjunction with each other.

Bus cycles are impressed upon the sub-buses. The standard VMEbus cycle is the READ/WRITE cycle, and can transfer 8, 16, 24 or 32-bits of data during every transaction. There are other bus cycles that are more specialized, or allow faster operation. These are summarized in Table 6.

The VMEbus specification allows different address and data widths to be used based on an application requirement. While all combinations are possible, certain combinations are more common than others. For example, A16/D8(O) is common for simple I/O boards while A32/D32 and A32/D64 are common for high performance SBC modules. As stated earlier A24 is usually found only on older 6U modules and is quickly being replaced by A32.

During the various enhancements to the bus in VME64 and VME64x, additional cycles were added. This is possible because VMEbus uses something called address modifier codes to 'tag' each bus cycle. As new cycles are developed, they are tagged with a new address modifier code, thereby insuring compatibility between modules. Future bus cycles are also planned.

The VMEbus specification allows full peer-to-peer multiprocessor capabilities. This is done with a flexible bus arbitration scheme that allows up to 21 masters in each system. A central bus arbiter, which is located in the first slot in the backplane (and is part of the VMEbus system controller), determines which master may use the bus. Arbitration methods include priority, round-robin and other scheduling algorithms.

Mechanical Hardware

There are two mechanical form factors for VMEbus modules. These are called single and double height modules. The smallest is the single height module, and connects to the P1/J1 connector. Traditionally, these modules can generate or accept up to 24-bit address and 16-bit data transfers. However, larger address and data transfers can new be achieved with A40/MD32 and 2eVME cycles (which are allowed under VME64 and VME64x standards).

Single height modules are commonly used if space is limited. Because of their size, they are also more resilient to shock and vibration than double height boards.

The larger and more popular size VMEbus board is the double height module. These are electrically compatible with single height boards (which use only the P1/J1 connector). Traditionally, 6U modules can generate or accept up to 32-bit address and 32-bit data transfers. However, the VME64 and VME64x specifications have introduced wider, 64-bit transfers in the MBLT and 2eVME cycles.

Single and double height modules are sometimes referred to as 3U and 6U boards. The 'U' is a unit of measure for the front panel, where each 'U' is equal to 1.75 inches.

VMEbus closely follows the IEEE Standard for Mechanical Core Specifications for Microcomputers (IEEE ). This specification shows the dimensions for a variety of board sizes (up to 12U x 400 mm), as well as sub-racks and other enclosures. The IEEE was later superseded by the IEEE .1-.

I/O cabling can be routed through the front panel of the module, or through the P2/J2 user defined I/O pins. Furthermore, the VME64x standard allows the use of a rear transition module. The rear transition module cards are defined by the IEEE .11 standard.

Some manufacturers also offer triple height (9U) boards. Strictly speaking, these modules are not supported by the VME64 specification. However, some users choose to mount 3U, 6U and 9U boards into a single sub-rack. Most Eurocard packaging systems will support multiple card sizes in a single chassis. For example, an adapter can be used to install a 6U board into a 9U card slot.

A new specification for 9U x 400mm size Eurocards has been completed by the VITA Standards Organization. It is called the VITA 1.3-.

The use of two standard card sizes has proven to be one of the biggest features of VMEbus. Users that have tight space requirements or severe shock & vibration constraints may choose the single height module. Users that have the space can go with the larger and more popular 6U card.

VMEbus Backplanes

VMEbus backplanes are available in lengths between one and twenty-one slots. On standard backplanes, boards are located on 0.8" centers (i.e. 0.8" pitch). There are three general types of backplanes available:

• Standard, 3-row connector backplanes.
• VME64x 5-row connector backplanes with 160 pin enhanced connector.
• VME320 backplanes.

Each of these styles of backplanes are available in 3U and 6U form factors. Furthermore, there are many options available on VMEbus backplanes. Some of the more popular options include:

• Active termination. Most VMEbus backplane are supplied with passive termination networks. These are are generally simpler and less expensive than backplanes with active termination. However, the passive termination networks do consume some power...typically about 1.3 A for a 6U backplane. Active terminators reduce this current to a few milliamps. Generally, both types of termination networks are equivalent in terms of signal integrity.
• Automatic chain. Backplanes are available that automatically close the interrupt acknowledge and bus grant daisy chains. These generally use a mechanical contact in the backplane connector, or an electronic closure method.
• Rear I/O connector shrouds. Standard, 3-row connector backplanes do not necessarily come with connector shrouds or specific connector hardware on the rear of the backplane. If you need this capability be sure to ask for it from the backplane manufacturer. VME64x backplanes are required to support the rear I/O transition modules specified by the IEEE .11 specification.
• Power supply connection. There is no standard way of connecting power supply leads to the backplane. Most use FASTON (spade terminal) connectors, screw terminals or custom connector systems.
• J2 high speed backplane. The J2 high-speed backplane offers extra rows of ground pins that straddle the J2 user defined pins (on the rear of the backplane). This is a specialty cabling option that is used to cut inductance on the cabling to the P2/J2 user defined pins. These backplanes are quite rare.

Multi-crate Operation

The maximum size of all VMEbus backplanes is 21 slots (19" width). The fundamental limits on the maximum length are how much drive current is available on each of the VMEbus boards, and the time delay down the backplane. If more slots are needed, there are generally two ways to handle the problem: (1) use a VMEbus-to-VMEbus bridge card set or (2) use a pair of 'reflective memory' cards. The bus-to-bus bridges essentially allow bus cycles on one backplane to appear on another. The reflective memory cards allow a memory segment on one backplane to appear on another. There are several vendors for each of these types of products.

Conduction Cooled VMEbus Modules

Another popular VMEbus card style is the conduction cooled module. These are used mainly in military and aerospace applications where convection cooling cannot be used. These allow heat to conduct through the printed circuit board or through a conduction plate on the backside. Special expanding card guides then transfer the heat through rails and then out to the chassis.

P1/J1 and P2/J2 Connectors

The VME64x specification describes three connectors for VMEbus modules. These are called the P0/J0, P1/J1 and P2/J2. The 'P' and 'J' nomenclature refers to the PLUG and JACK connectors, which reside on the bus module and backplane respectively.

Originally, all VMEbus products used a 96-pin DIN connector. These connectors are very reliable, are low cost, and are available from a variety of suppliers. The VME64 and VME64x standards now permit a new 160 pin connector, which is shown in Figure 1. The 160 pin connector has thirty-two additional pins located on both sides of the original DIN connector. These are designated as the 'z' and 'd' rows. The new connector was added for two reasons:

• Additional signal connections allow more backplane functions.
• Additional ground pins suppress ground-bounce and cross-talk.

Four pre-charge pins are provided on the new connector. These form a make-first, break-last connection. This feature is intended for hot-swap boards, and are used to pre-charge bus interface circuitry.

These connectors are available from Harting Electronik and AMP Inc.

The 160 pin connector is completely optional in the VME64 standard. The connector itself is not needed to support any of the newly defined functions. For example, it is not needed to support the new sixty-four bit address and data cycles. However, in VME64x boards and racks the new connector is needed to support additional pins such as +3.3V power and geographical addressing.

The 160 pin connector is designed to allow full forward and backward compatibility: older legacy boards will fit into new backplanes (and vice-versa).

Description of the P2/J2 user defined I/O pins.

Figure 1. Enhanced 160-pin connector.

P0/J0 Connector

The VME64x standard allows the use of a 95 pin P0/J0 connector. This connector is placed between the P1/J1 and P2/J2 connectors.

The P0/J0 connector was added because of the higher I/O demands now placed on VMEbus systems. This is especially true in military and telecom applications. For example, in many applications the use of front panel cables are frowned upon because:

• There is not very much room for connectors on the front panels of conduction cooled boards.
• Front panel cables are often susceptible to shock and vibration problems.
• Bus modules are harder to replace when cables are attached to the front panel.

The P0/J0 connector conforms to the IEC -4-101 standard. These connectors are available from AMP Inc., and ERNI components. Unlike the DIN connector family, they include specifications for mating impedance and maximum capacitance. This makes them an excellent choice for high speed signals.

The VME64x standard also allows the use of custom connectors in the region between the P1/J1 and P2/J2 connectors. For example, a coaxial cable or fiber-optic connector could be used. This practice is not recommended, as the board may not be compliant with VME64x backplanes. However, if a custom connector must be used, then the VME64x standard recommends that the front panel keying mechanism be installed to prevent installation of an incompatible module.

I/O from the P0/J0 connector can be routed:

• Out the rear of the backplane using ribbon cable connectors.
• Onto a rear transition module (plug-in unit).
• Bussed across the backplane.

At first glance it would appear that all of these options on the P0/J0 connector could lead to incompatibilities. However, this problem is no worse than on the P2/J2 user defined pins. Also, VME64x module keying can also be used to insure that VMEbus modules are placed into compatible backplane slots.

Mezzanine Modules

Mezzanine modules are a popular way to customize a VMEbus card. These cards generally fit on top of a common base board. This allows users to 'mix-and-match' the I/O functions that they need. The mezzanine modules have become very popular in recent years. That's because they save a great deal of hardware development time, and inventory. Software development is also faster and less expensive.

While the mezzanine module concept has been around for many years, the VMEbus mezzanine industry has been fragmented because of all of the types of mezzanine cards. This situation has improved steadily as new standards have been adopted. This FAQ will not attempt to describe all of the types of VMEbus mezzanine cards.

There is currently a plethora of mezzanine standards that are available. Currently, there are over 30 types available for VMEbus modules. However, two types of mezzanine modules seem to be gaining a substantial foothold. These are the CMC/PMC and IP (IndustryPack®) bus modules.

For example, the CMC/PMC form factor uses a common mechanical footprint for VME64, Multibus I, Multibus II, Futurebus+ and generic platforms. The CMC (or Common Mezzanine Card) part of the system describes the mechanical form factor, which is shown in Figure 2. Impressed upon the connectors is a local PCI (Peripheral Component Interconnect) bus, hence the name CMC/PMC.

Figure 2. Common Mezzanine Card (CMC) concept.

Where to Obtain Copies of the VMEbus Specification

Copies of the VMEbus specifications are available from a variety of sources. That's because VMEbus has undergone various revisions through different organizations.

ANSI/VITA 1- (VME64), ANSI/VITA 1.1- (VME64x) and Many Others

VITA

ANSI Approved Versions

American National Standards Institute (ANSI)
11 West 42nd Street
New York, NY USA
: (212) 642-; FAX: (212) 398-

IEEE - (VMEbus) and IEEE .XX Mechanical Standards

IEEE Service Center
Publications Sales Department
445 Hoes Lane; P.O. Box
Piscataway, NJ USA -
: 800-678-

Retired and Obsolete Documents

IHS Global Engineering Documents
15 Inverness Way East
Englewood, CO USA
: (303) 792-

Additional Information

Application Notes

VMEbus related application notes

Obsolete VMEbus Equipment, Repairs

Obsolete VMEbus equipment (new or used) can be obtained from a variety of sources, including the following firms (note: these firms are not VITA members and this list is provided for convenience only):

Are you interested in learning more about Subrack Kit for Backplane? Contact us today to secure an expert consultation!

• GDCA
• Innovative Research
• Sun Harbor Sales