Author: Manfred Schmitz, CTO MEN Mikro Elektronik
CompactPCI Serial – PICMG CPCI-S.0 – is mechanically based on IEC1101, the standard for 19-inch systems and Eurocards. This guarantees that mezzanine modules that have been designed for these boards, and are indirectly based on the IEC1101 standard, are also compatible with CompactPCI Serial.
The most important types of such mezzanines are PMCs, XMCs and M-Modules. All of these modules fit on Eurocards. A single Eurocard can accommodate one PMC/XMC or one M-Module, while a double Eurocard can carry 2 PMCs or XMCs, or 4 M-Modules.
Because of the connector types used for CompactPCI Serial, the space usable for components is a little bit smaller than with parallel CompactPCI and VMEbus boards. This is why for CPCI-S.0 the P1 connector, being the only connector necessary for peripheral boards, was placed at the lower edge of the 3U board. As this connector is only 13 mm wide and a margin of 2.5 mm each is reserved for support rails, this leaves a width of 82 mm that is usable for components. A PMC/XMC with a width of 74.5 mm comfortably fits on the board. Of course, this also goes for an M-Module with 53 mm width.
The same is true for double Eurocards – basically. Since 6U boards expand 3U boards at the lower edge, P1 is located quite at the center of the 6U board. This has no importance for PMC/XMC modules. Two of these modules find space on a double Eurocard. A maximum of three M-Modules are possible on a 6U board.
The electrical control of mezzanine modules that are based on modern serial interfaces is especially easy. For XMC modules, you only have to connect the right lines and generate the power supply locally. Of course, hot-plug support is possible, too. For modules that are based on older, parallel buses, you need a bridge. PCIe-to-PCI bridges for PMC modules are available as standard components. For M-Modules you will rather choose FPGA-based solutions.
Three aspects played a major role for the definition of the CompactPCI Serial standard: the usage of the most up-to-date technologies (serial interfaces instead of parallel buses), cost-optimized, robust design, and backwards compatibility to existing solutions. The way PMC and XMC modules can be used in CompactPCI Serial systems impressively illustrates this.