RMC Register Map (Modbus Plus)

Tip: RMCWin's Address Tool provides an easy way to identify addresses in the RMC. Simply open the Address Tool and then move the cursor to any field in RMCWin that represents an RMC Register, and the Address Tool will display the address in the address format of your choice. See Address Tool for details.

The RMC module has 64K (65536) 16-bit registers that can be read from or written to over Ethernet, Modbus Plus, and PROFIBUS-DP. Each register is assigned an address. However, under the different communication methods, different addressing schemes are used. This topic describes the addressing through Modbus Plus. For details on addressing from other modules refer to the following topics:

• RMC Register Map (Allen-Bradley)

• RMC Register Map (Automation Direct)

• RMC Register Map (Modbus/TCP)

• RMC Register Map (Omron FINS)

• RMC Register Map (Siemens TI505)

• RMC Register Map (Siemens S7)

• RMC Register Map (PROFIBUS-DP Message Mode)

To communicate with any Modbus Plus device, the RMC requires the Modbus Plus communication module. Under Modbus Plus, the RMC registers are addressed as values 1-65536. They can be thought of as equivalent to Modicon Holding Registers. For details on reading and writing these registers, see Reading and Writing Modbus Plus Registers.

Note: When entering register addresses into an MSTR block, do not add 40000 or 400000 to indicate holding registers. MSTR blocks expect the addresses to start at 1, rather than 40001 or 400001.

Status Registers:

These registers can only be read; writes are ignored.

Command Registers:

These registers can be read or written.

Parameter Registers:

These registers can be read or written. Changes to these registers do not take effect until a Set Parameters (P) command is executed.

Event Step Table Registers:

These registers can be read or written.

Input to Event Table Registers:

These registers can be read or written.

Status Map Registers:

These registers can be read or written, although you should not manually change the values in this table. You should use the Status Map Editor to change this table and then download it to the RMC. You may then read this table into the PLC and send the table to the RMC each time the PLC is restarted.

Plot Type Registers:

The plot type registers can be read or written. The values that are read indicate the extra plot information in the current graph. The values written to these registers tell the controller which extra plot information to obtain on the next plot. For these registers, the following values are used:

• 0: Extra position precision

• 1: Command and Command Value

• 2: Event Step and Link Value

• 3: Raw Transducer Counts

• 4: Internal Target and Actual Speeds

• 5: Integral Drive

For more information on these four types of plot information, see Selecting the Data to Plot and Reading Plots from the Communication Module.

Digital (Discrete) I/O Registers:

These registers indicate the current state of the digital inputs and outputs. These registers may only be read; writes will be ignored, as this product does not support forcing inputs or outputs.

Because different PLCs label bit numbers differently, the following chart is provided to show the mapping between the devices:

The bit numbers listed in the table below are in RMC format (0 is LSB, 15 is MSB):

Plot Time Registers:

The Plot Time interval is configurable on the RMC. This interval indicates the number of control loops between each sample in a plot. Therefore, if the control loop is 0.976ms (e.g. RMC100-M1), this indicates roughly the number of milliseconds between samples. If the control loop is 1.953ms (e.g. RMC100-M4), this indicates half of the number of milliseconds between samples.

These registers may be read or written. When read, they indicate the plot interval of the currently gathered plot. When written, they set the plot interval the RMC should use for the next plot it will gather. When the RMC starts the next plot, it copies the requested plot interval into the currently used plot interval.

Last Parameter Error Registers:

Note: To use these registers through Modbus Plus, you must have RMC100 CPU control firmware dated 19990819 or later.

Each of these read-only registers holds the number of the last parameter error generated on an axis. This is useful for determining the cause of the Parameter Error bit in the status word. For a description of the values read from these registers, see Parameter Error Values.

Firmware Date Registers:

Note: To use these registers through Modbus Plus, you must have RMC100 CPU control firmware dated 19990819 or later.

These read-only registers hold information about the firmware versions in the RMC100 CPU module. The Boot and Loader firmware versions have no effect on the actual performance of the RMC and therefore can usually be ignored.

Reserved Registers:

Reading these values will return zero, and writes are ignored.

Spline Download Area:

These registers are write only. Reading them will return zero. This area is used to download intervals and points in a spline. This is a much more efficient alternative to using individual New Spline Point and Set Spline Interval/End Segment commands. For details on using this Spline Download Area, see Downloading Splines to the RMC.

Plot Registers:

These registers can only be read; writes are ignored.

Note: Reading plots is not a trivial task; for further details, see Reading Plots from the Communication Module.

Copyright (c) 1997-2015 by Delta Computer Systems, Inc.