Since the C/MRI was first introduced in the February 1985 issue of Model Railroader it has been implemented on a thousand railroads with a myriad of different approaches. It’s hard to beat the system for implementation simplicity, flexibility, prototype fidelity, reliability and cost effectiveness. Over the years the system has received several technology updates with the latest being the introduction of eight new circuit boards. These new boards provide much improved capability while making interfacing easier and more affordable. Here’s an overview of the new cards:
. SUSIC
This new Super Universal Serial Interface Card provides an upgrade of the original design USIC - the one using the 68701 chip. The new Microcontroller based SUSIC plugs into an I/O motherboard, as does the original USIC, for interfacing up to a total of 64 digital input and digital output cards. The SUSIC is smaller, faster, much more capable and costs less than the original USIC.
. SMINI
This new Super Mini-node card combines all the advanced features of the new SUSIC with 48 output and 24 input I/O lines. It's really a single card providing a complete standalone serial node with 72 I/O lines. Cost for do it yourself assemblers can be as low as $1 per I/O line.
. DIN32
This new digital I/O card incorporates 32 input lines. The resulting smaller card provides 33% more I/O than the previous DIN card while plugging directly into the I/O motherboard. Each card is DIP switch addressable up to 64 cards per node. The card includes optional built-in input line filtering.
. DOUT32
This new digital I/O card incorporates 32 output lines. The resulting smaller card provides 33% more I/O than the previous DOUT card while plugging directly into the I/O motherboard. Each card is DIP switch addressable up to 64 cards per node. Drive capability has been increased with less current draw per card. Each of the card's four 8-bit ports is separate ly configurable to support either standard current sinking or current sourcing.
. TEST32
This new system output diagnostic test card plugs directly onto the new DOUT32 card to test all 32 output lines. An easy to read port and bit legend is printed directly on the card eliminating the need for the separate label panel used with the previous test cards. Two-lead bi-color LEDs are employed so that the same card can test current sinking as well as current sourcing outputs. Employing the TEST32 card, followed by using the standard wraparound test cable makes it a snap to completely test the entire C/MRI system.
. IOMBX
This newly expanded I/O Motherboard provides 15 card slots as compared to the 13 provided by the previous IOMB. The 40-pin header, included with the IOMB, is deleted from the IOMBX in favor of adding the additional card slots. Thus, the IOMBX is the preferred motherboard for all USIC applications while the IOMB is still required when using the IBEC.
. RS485
This new RS232 to RS485 conversion card replaces the previous RS422 conversion card. Plus and minus 12Vdc power is no longer required as everything works off a standard +5Vdc supply connection. The new RS485 card retains the same advantages use of the two data direction monitoring LEDs and works with both the RS422 and RS485 standards. Line termination resistor networks are included as an integral part of the card's design.
