ESMexpress® versus ESM™

ESM™ is MEN's first SOM concept introduced in early 2003, being one of the first SOMs on the market.

Unlike ESMexpress®, ESM™ is based on the PCI bus. ESM™ is a company standard that already aimed at the idea to be open towards different processor architectures.

The ESM™ specification defines one 71 x 149 mm form factor which is very close to the PMC format. In fact this allows to use up to three ESMs on a 6U carrier card (e.g. CompactPCI® or VME), or for example one ESM™ and two PMCs.

ESMs can be used on Eurocard carriers but also on customized carrier cards or even completely stand-alone. This is because every ESM™ has its own power supply and comes with a set of front connectors depending on the module functionality.

One major difference compared to ESMexpress® is the support of an FPGA directly on the CPU module to allow user-defined I/O extensions in a very flexible way.

This made the pin-out between ESMs with customized IP cores in FPGA different by nature. ESMexpress® now features a fixed pin-out in order to be compatible with any carrier board.

If at all needed, the FPGA functionality has been moved to the carrier board. FPGAs are meanwhile connected via a PCI Express® link which is not only faster but also reduces the number of pins formerly reserved for FPGA functions on the COM connector.

Already, ESM™ modules have used a robust PC/104-type connector and all modules have been designed to operate in harsh environments in terms of temperature (up to -40 to +85°C), soldered components to withstand shock and vibration, and they are all ready for conformal coating. With ESMexpress® now the idea of having a real rugged COM standard has been optimized without compromises.

Unlike ESM™, the new ESMexpress® standard comes with a cooling concept which is solved for -55 to +125°C based on conduction cooling, a completely sealed and EMC-proof metal housing, and a rugged connector that has been approved by major railway and avionics companies.