M-Module Mezzanine Bus Information

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M-Module Mezzanine Bus

Mezzanine boards are small form factor cards designed to plug onto larger form factor boards.
The larger main boards can be designed to support one or more Mezzanine boards. Not all mezzanine formats are supported by all host boards.
M-Module is still an active standard, but it was first released in 1997, so it's some what dated [or out-dated].
Two card variants are possible; a M-Module card and an MA-Module card [which differ by the connector].

In addition to the single wide form shown above, M-Modules can be developed into double, triple and quadruple wide configurations.
M-Modules are sized such that 4 cards will fit onto a 6U VME module and 2 onto a 3U VME module.
Conveniently, because of the way other backplane standards have evolved, 4 units easily fit the front panel space in VXI and 6U cPCI/PXI.
While 2 modules will fit in the font panel space of 3U cPCI/PXI and up to 8 will fit in a 1U LXI rack mount carrier.

M-Modules are designed to extent to the front-panel of the main board, and have their own front panel.
A connector may also be used that is within the limits of the M-Modules front panel dimensions.
A 25 pin D-Sub connector is suggested as a possible connector style but is not made a requirement.
Both the M-Module and the base-board would need to have a 24 pin header [peripheral connector] to support the front panel connector.
The signals from the front panel would be routed to the header and would than be passed to the base board.
Pin 13 of the receptacle [Module] or pin 1 of the plug [Baseboard] is not bussed between cards.

M-Module Description

The M-Module defines the electrical and Mechanical characteristics of the bus.
M-Modules utilize 2-row [40-pin] connectors, while MA-Modules have 3-row [60-pin] connectors for module to main board communication.
The boards come as single or double width sizes [as do most other mezzanine card standards].
The M-Module [Mezzanine-Module] Card size is 52.9mm x 148.3mm, there are other board sizes
The MA-Module [Mezzanine Addition-Module] Card handles more signals [by adding a third row of connectors].
The M-Module uses an 8-bit, 16-bit or 32-bit data bus, and an 8-bit or 24-bit address bus.
An asynchronous SYSCLK of 16MHz is required. Power supply voltages of +5v [1000mA], and +/-12 volts [200mA] are required.
Standard TTL logic levels are used, more detail on TTL devices under the Design icon below.

Editor note; The standard reads just like the VME spec does, and appears to operate or handshake just as VME did.
So, transfer rates will be slow when you considered the hand-shaking and/or the 16MHz clock rate.

ANSI/VITA 12-1996
Rows A and B correspond to an M-Module, while row C is the optional MA-Module addition.
Row A is internal to the card, row B in the center, and row C nearest the edge of the card.
The front panel connector, if present on the board is not shown in the table.

M-Module Board Manufacturers

C&H Technologies Inc. {Switching Modules, Measurement Modules, Serial, Digital & Prototyping}

N.A.T. {Ethernet communications on M-Module, Serial I/O M-Module, ISDN M-Module}

Even though the M-Module was released in 1996, there are still companies producing product.
Products are produced as modules or carrier cards, or carrier units that accept plug-in M-Modules.
Manufacturers of M-Modules [not a big list, but there still a few vendors]. A Baseboard would be some other card format [VME/VXI/cPCI].
Use the links at the top of the page to review additional descriptions and styles of Mezzanine Cards or Daughter Cards.
Most but not all Mezzanine Cards use different board form factors or card dimensions and they all have different Electrical Interfaces.

As of 2012, ANSI / VITA12 is still listed as a valid standard, so it's still approved and has not yet been withdrawn.
So in reality a company could still design compliant boards which adhere to the standard, although there may not be much of a market.
Of course the transfer speed between the module and the baseboard would also be a limiting factor, and would not compare well with newer mezzanine boards.
There would also be a question as to how many new VME baseboards are designed with a M-Module slot, not many would be the assumption.
Why would a company spend the research dollars to add a mezzanine slot that was over 10 years old.
So if no new baseboards are being produced, that leaves only legacy or pre-existing boards [main-boards].
Basically this comes down to a niche market setup to handle replacement mezzanine cards as they malfunction.

Topic Navigation > Engineering Home > Interface Buses > Mezzanine Buses > M-Module Specification.

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