Interoperability Considerations Between Different Host FMC and FMC Mezzanine Vendors
May 02, 2011 | BY: Jeremy BanksDownload PDF
I/O mezzanines promise flexibility and a reduced system footprint. Most mezzanines use standard bus based interfaces or a proprietary format. Aimed at FPGA centric solutions, the FMC (FPGA Mezzanine Card- ANSI VITA 57.1), is different. In the same way as one might strip out unnecessary weight in a car aimed for racing, the FMC is a performance solution that strips away unnecessary generic interfaces for direct FPGA driven I/O. But that requires knowledge to achieve the desired performance and to ensure the host and FMC module will work well together. This paper outlines some of the considerations in order to assess and the ensure that the host and module will integrate.
What are FMCs?
New generations of FPGAs present developers with a level of processing performance and potential I/O bandwidth that cannot easily be matched by conventional CPU configurations. The FPGA mezzanine card directly addresses the challenges of FPGA I/O by solving the dual problem of how to maximize I/O bandwidth while still being able to change the I/O functionality. The FMC format offers an elegant solution because they only need to deal with the I/O devices, such as ADCs, DACs or transceivers. FMC modules have no on-board processors, bus interfaces or bridges, such as PCI as required by the PMC module format. FMC modules directly connect the I/O devices to the host FPGA.
This directness of linking physical I/O devices on one card (the FMC mezzanine) and the FPGA (the host), on another means that the probability of immediate interoperability between host cards with no code changes is low. However, the advantages of FMCs for high performance applications are considerable, including high bandwidth, low latency interfaces, lower power and more I/O real estate. At around half the length of a PMC, FMCs are small, but not at the expense of functionality because FMCs don't need bridges, memories, etc.
The speed and number of connections that an FMC format module uses, together with direct FPGA to I/O devices means that the FMC format is particularly suited to applications benefitting from multi-Gbyte per second I/O with low latency. Examples of such applications are direct RF I/O, radar, Signals Intelligence (SigInt), satellite communications and Electronic Counter-Measures (ECM).