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.

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In fundamental terms the SMINI-node provides an update to the previously offered USIC combined with the features of two digital output cards and a digital input card and places them all on a single card. The resulting multi-function interface card provides 48 outputs and 24 inputs. Up to 128 Mini-node cards can be connected together in any one system.

The SMINI and SUSIC nodes can be integrated in with all previous C/MRI hardware. For highly modular layouts using a SMINI per modular is ideal. Many larger conventional layouts typically use a SUSIC node at a dispatcher CTC panel and SMINI nodes out along the route. Other railroads frequently employ SUSIC nodes at major rail junction interlocking plants, terminal areas and large staging yards.

Each SUSIC node has an expanded limit of 64 I/O card for a count of 2048 I/O lines compared to 72 I/O lines for the SMINI. The I/O limit for all 128 nodes using the SUSIC card is 262,144 and with all SMINI nodes is 9,216.

Small railroads may only need a single SMINI while others can use several SMINI nodes combined in with possible SUSIC based nodes handling areas requiring larger I/O concentrations.

Summarized features of the new SMINI, and SUSIC include:

1. Both cards utilize the same Bruce Chubb programmed PIC16F877 Microcontroller, available directly from JLC Enterprises. This improvement provides a state of the art update yielding great system simplification, higher speed and a significantly reduced cost. With the FLASH memory capability of the 16F877, it is relatively easy for the user, a third party or JLC to make system updates.

2. Both cards provide for serial connections to the computer being either RS422 or RS485 for creating a multi-node distributed system or RS232 for easy single-node startup systems. All cards include dual RS485 connector sockets for easy daisy chaining between multiple-nodes. The whole system requires only a single +5Vdc supply so there is no need to couple in plus and minus 12Vdc even when using the RS232 option.

3. Both cards provide easy built-in optimized line termination capability for RS485/RS422. You simply plug in a connector shell with two resistors into the second RS485 connector in the last card. All other terminations are built right into the RS485 conversion card. Such terminations yield enhanced electrical noise immunity especially important with operation associated with pulse-type command control systems like DCC and Rail Command.

4. Both cards incorporate a 4-segment DIP switch for selecting baud rates of 9600, 19200, 28800, 57600, and 115200 bits per second. On any system, higher baud rates result in more frequent transmission errors and it is always best to operate at the lowest baud rate that produces fast enough system response. Using the C/MRI's built-in baud rate selection switch it's easy to achieve that optimized trade-off between high-speed operation and error-free operation as tailored to fit each individual application.

5. Both cards incorporate a 7-segment DIP switch dedicated to setting each card's unique address from 0 to 127 yielding a maximum total node count of 128.

6. Both cards incorporate 3 built-in system performance monitoring LEDs (red, yellow and green). These provide easy to use operational diagnostic capability. The error monitoring codes have been expanded over those provided with the original USIC design.

7. A single 4-wire cable is the only connection required between nodes and the nodes can be distributed anywhere within a 4000ft range. All local wiring to signals, detectors, grade crossing devices, panel components, reversing relays, switch motors, and so forth simply connect to I/O pins at the nearest node. Wiring can't be made much simpler.

Additional features for the I/O lines provided by the SMINI, DIN32 and DOUT32 cards are summarized as:

8. Each of the C/MRI standard output lines (6 ea. 8-bit ports on SMINI and 4 ea. on DOUT32) feature an open collector transistor output for maximized reliability driving loads drawing up to .25A. If you ever blow a part by accidentally shorting an output, or driving a too heavy load, the cost of replacing the transistor is insignificant, about 5 cents. An even bigger advantage is that you know which part needs replacing since it is right in line with the failed I/O line.

9. Each of the output ports is configurable for current sinking or current sourcing. This provides direct drive capability for both 2-lead and 3-lead tri-color searchlight signal LEDs. In addition to supporting the 3-lead LED case, including the current sourcing option becomes especially important to efficient wiring when driving any signaling or other accessories where the common connection between loads is wired to ground.

10. Each of the C/MRI standard input lines (3 ea. 8-bit ports on SMINI and 4 ea. on DIN32) feature optional input line filtering for maximizing immunity to electrical noise frequently encountered with pulse-type command control systems such as DCC and Railcommand.

Additional features unique to the SMINI are summarized as:

11. Independent of whether or not input filtering is selected each input line is properly buffered before it reaches the PIC16F877 Microcontroller. These relatively inexpensive buffer ICs, mounted in sockets for easy replacement, perform as fuses to prevent inadvertent higher than 5Vdc connections on any input line from blowing the more expensive Microcontroller. Such actions can reduce frustration as well as save many dollars over the life of a system.

12. To further reduce cost, the SMINI can be assembled with less than the full complement of parts for nodes requiring less than the provided 72 I/O line capacity. Where more lines are required one can simply add another SMINI. Alternatively, at nodes where considerable I/O is required, simply employ the new SUMB with its compliment of I/O cards or use the SUSIC plugged into an IOMBX. This way it's easy to tailor any node to best meet any required number of I/O lines.

13. The software built into the SMINI can automatically oscillate adjacent outputs for creating the yellow aspect when using 2-lead LED searchlight signals. The duty cycle is adjustable for improving the quality of the yellow. The 3-lead type searchlight signal LEDs are best handled by simply configuring standard outputs to current sourcing or by using a special resistor hookup to current sinking outputs.

14. You don't need a separate power source to drive the SMINI. Simply connect it up to the same +5Vdc supply that drives everything else in the node containing the SMINI.

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Forward and backward compatibility is a great feature of the C/MRI. It’s easy to mix and match components however you desire to form each node. For example you can set up all nodes as single card SMINI-nodes. Or you can combine in one or more nodes using the new SUSIC card with an IOMBX. Simply pick the best node combination to meet your particular needs. The only restriction being that the total node count not exceed 128. With up to 128 nodes possible, overall layout wiring can be truly minimized to whatever reduced level you desire.

Any combination of Mini-nodes and Maxi-nodes can be connected to existing C/MRI nodes featuring the original design USIC. However, including the original design USIC, with the 68701 chip, one is limited to baud rates of 19200 or less and the original 16 nodes rather than the 128 provided when all nodes make use of SMINI and SUSIC cards. Also, new SUSIC and the SUMB nodes can drive any combination of the original 24-line DIN, DOUT, CIN24 and COUT24 cards.

You can use the new SUSIC card to speed up the operation of your present USIC based distributed system. To do so simply unplug the present 68701 based USIC card and plug in the new 16F877 based SUSIC card. To check out the system keep the baud rate the same. With check out complete, then set the baud rate, to increasing values, at the PC and the USIC cards, until you achieve the desired higher-speed operation.

All the new designs are available as ready-to-assemble cards, as complete kits and as fully assembled and tested units. For making it easy for do it yourselfers, all C/MRI circuit boards feature large pads and wide heavy-duty traces with no traces are routed between IC pads. This standard JLC design practice makes for very easy soldering and board repair. The resulting boards are always a bit larger. However, the resulting ease working with a somewhat larger board with its additional spacing between parts is a significant advantage during card assembly, testing, debug and repair.

To further ease assembly, testing and debug, all the I/O parts on the SMINI are in alignment with the card's I/O pins, including each output transistor. The same is true for the important I/O buffers and input line filtering components. Automated system testing capability is provided using the TEST32 card and the wraparound test cable as used with previous C/MRI hookups along with the automated test software included as part of the software disk provided with the C/MRI User's Manual.

The C/MRI User's Manual V3.0 as well as the Railroader's Application Handbook V3.0 provide extensive software coverage including updated standard serial protocol subroutines, real-time software control, multiple application examples plus system test programs, and automated diagnostics. All software is incorporated in a 3.5" disk enclosed with the User's Manual. To fit the background and needs of different readers, examples are included in an assortment of languages including BASIC, QuickBASIC, Visual Basic, Pascal and C++.

The C/MRI works great with all Digital Command Control (DCC) systems. The Railroader's Applications Handbook provides extensive details on how to interface the C/MRI with DCC systems including the specifics as they relate to the different DCC manufacturers. The C/MRI can handle such functions as trackside signaling, staging yard control, junction interlocking, control panel interfacing, train dispatching, layout and room lighting, hump yard control, automatic turntable indexing, engine assignment to throttles, display mode operation or fully automated operation. If you are not into modifying all your engines for Command Control, the C/MRI presents alternatives via Computer Cab Control (CCC) and Computer Block Control (CBC) - both requiring no engine modification.

An advantage to expanding your present C/MRI system with JLC provided boards is that you are totally assured that every new item is 100% compatible with all other JLC provided components. Also, every C/MRI component item you purchase from JLC is 100% supported by the Bruce Chubb created quality documentation you have come to expect as standard. There's no going back and forth between different suppliers when your total C/MRI system is 100% backed by the JLC 100% C/MRI compatibility guarantee.

Additional information covering model railroading applications of the C/MRI can be found in The Railroader's C/MRI Applications Handbook V3.0. It contains over 500 pages of additional model railroading material. The handbook doesn't replace having a copy of the C/MRI User's Manual V3.0 nor does having the User's Manual replace having the Railroader's Applications Handbook. The two books work together to tell the whole C/MRI story. The handbook assumes that readers already have cards available, either they assembled them or purchased them assembled and tested, and thus devotes its full attention to railroad system applications.

For readers desiring to get started applying the interface, it is easy to build up your own C/MRI boards using the ready-to-assemble circuit cards available from JLC Enterprises using the order blank provided. Recommended source lists are provided for easy location of all electronic parts in Version 3.0 of the C/MRI User's Manual.

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