Diamond Systems MRC-424-XT PC/104-Plus Module with Quad 10/100 Ethernet and Digital I/O

Rugged systems often need more network connections than the host SBC provides, and sometimes a way to daisy-chain equipment along one Ethernet run. The MRC-424-XT, Diamond Systems’ Mercator II module, adds four 10/100 Ethernet ports and 24 digital I/O lines to a PC/104-Plus stack, which can remove one board from the stack compared with separate Ethernet and digital I/O modules.

The Ethernet ports are driven by two dual-port Micrel KSZ8842 MAC and PHY controllers on the PCI bus, two ports per chip, and they are NE2000 compatible. Each chip has its own MAC address, so the host sees two active Ethernet interfaces. On each chip the second port works in switch fashion, with one port acting as an uplink to a network while the other communicates on it, which allows networks to be daisy-chained through the module.

Each port of the MRC-424-XT connects through a pin header with its own activity LED, and Diamond’s C-PRZ-02 cable provides a panel-mount RJ-45 jack. The 24 digital I/O lines sit on the ISA bus, based on an 82C55, with ports A and B programmable as all inputs or all outputs and port C in 4-bit groups, plus 10 kΩ pull-up resistors that can be enabled or disabled. Eight base addresses are jumper-selectable, and the PCI slot for each Ethernet port is set the same way. The DS-MPE-GE210 adds a single Gigabit port through a MiniCard socket, and the EMM-8PLUS-XT adds serial ports to the same PC/104-Plus stack.

The module runs from 5 V DC and follows the PC/104-Plus standard, with both ISA and PCI stackthrough headers installed. The MRC-424-XT operates from -40 to 85 °C at 5 to 95% humidity, non-condensing, and can be custom-configured with 0 ohm resistors in place of jumpers for high-vibration installations such as vehicles.