Author: Manfred Schmitz, Technical Director of MEN Mikro Elektronik
PICMG 2.30 is an extension of the CompactPCI® standard PICMG 2.0 and is available as a draft at present. The CompactPCI® specification permits to lead user I/O to the backplane via 3U boards on the 32-bit system slot. These signals are often used to provide the modern serial buses like PCI Express, SATA, USB and Ethernet. Until now no standard existed, which led to incompatibilities between the boards of different manufacturers. This is particularly detrimental if rear I/O signals like PCI Express are used directly to build hybrid backplanes for CompactPCI Express.
CompactPCI Plus IO – PICMG 2.30 – remedies this. It defines the pin assignment for four PCI Express links, four USB interfaces, four SATA interfaces and two Ethernet channels. In order to ensure electrical functionality a completely new but 100\% compatible connector by 3M has been introduced as J2 connector. It is equipped with an additional internal shield so that it is able to support the required high freqencies even without additional ground pins.
The pin assignment has been chosen in such a way that a 32-bit PICMG 2.30 board can function in a 64-bit backplane. However, the rear I/O pins cannot be used in that case, because the pins are needed for the 64-bit extension. 64-bit PCI transmissions are not possible. In order not to lose all degrees of freedom, PICMG 2.30 still allows the usage of free pins for user-defined I/O. If you require only one Ethernet interface on the backplane and want to lead LVDS to the back for controlling a monitor, you can use the free pins of the second Ethernet interface for LVDS. The assignment has to be chosen in such a way though that an Ethernet device which might be connected to LVDS cannot be damaged.
CompactPCI PlusIO - PICMG 2.30 - is a 100\%-compatible extension of PICMG 2.0, which fits modern chip technology and enables the migration to new standards like CompactPCI Plus. Future CPU boards should be developed with regard to PICMG 2.30 compatibility. This ensures that boards of different manufacturers are inter-exchangeable and guarantees compatibility to following standards like CompactPCI Plus.