Indirect Data Map

The Indirect Data Map maps data registers from anywhere in the RMC to a single area. This allows scattered data items to be consolidated for efficient communications. Instead of reading and writing to many locations, a single read and single write can be made.

Example:

Perhaps you wish to read 5 registers in the RMC75E via the Allen-Bradley CSP protocol (DF1 over Ethernet). These registers may have addresses F8:0, F8:8, F9:0, F9:8, and F56:0. Reading these would require several reads, and would not be very efficient. By using the Indirect Data Map, you can assign these registers to F18:0 to F18:4. Now only one read of 5 registers is required, which is much more efficient.

The Indirect Data Map is used for EtherNet/IP I/O, PROFINET, and PROFIBUS. See those topics for details on how the Indirect Data Map is used with those protocols.

When to Use the Indirect Data Map

The Indirect Data Map can be used for all protocol address types supported by the RMC. The Indirect Data Map is particularly useful for data that is frequently communicated, such as RMC status being read by a PLC. Here are particular details on when it must be used or isn't necessary.

PLCs

In general, anytime a PLC is communicating with the RMC, the Indirect Data Map should be used in order to achieve efficient communications. It is especially useful for data that is continuously transferred.

HMIs

When communicating with the RMC from an HMI, the Indirect Data Map is usually unnecessary because the HMI can address the RMC registers directly, and HMI communications are often not efficient to begin with.

Using the Indirect Data Map

The Indirect Data registers can be mapped to any registers in the RMC. Thereby, the values from the mapped registers in the RMC can be read from and written to by writing to and reading from the Indirect Data registers.

To set up the Indirect Data Map:

1. Open the Address Maps editor and select the Indirect Data Map.

2. In the Map To column of an Indirect Data Map row, click the ellipsis button to browse to the RMC register you want to map. You can map as many of the Indirect Data Map entries as you would like.

3. Click the Download button to download the changes to the RMC.

4. Now, with your PLC or other host controller, you can read or write your data directly from the Indirect Data registers. Notice that if a mapped register is read-only, you cannot write to it.

Note:
Do not write to registers in the Indirect Data Map that have not been mapped. This may unnecessarily fill up the Event Log with errors.

Example

The user would like to put some of the RMC75 registers in the Indirect Data Map so that the communications can be more efficient. The user decides to put the following registers in the Indirect Data Map:

• Axis 0 Status Bits

• Axis 0 Error Bits

• Axis 0 Actual Position

• Axis 0 Actual Pressure

• Axis 1 Status Bits

• Axis 1 Error Bits

• Axis 1 Actual Position

• Axis 1 Actual Pressure

The user then sets up the Indirect Data Map as shown below:

To read the data from the mapped registers, read from F18:0 to F18:7. Now, instead of reading 8 registers in various locations, the user can read 8 registers in one block. Notice that if a mapped register is read-only, you cannot write to it.

Choosing the Address Format

The addresses of the registers in the Indirect Data Map are displayed in the Reg # column. To change the address format, right-click any cell in the Reg # column, choose Address Formats, and choose the desired format.

Advanced Details

Structure of Indirect Data Map Registers

The Indirect Data Map consists of two arrays of values. The first array is called the Indirect Data Map Definition, which holds register addresses that each entry in the second array (Indirect Data) represents. The Indirect Data Map Definition can be used for both readable and writable registers.

Note:
During normal communications with the RMC, it is the Indirect Data registers that should be written or read, not the Indirect Data Definition registers.

Changing the Indirect Data from a PLC

Typically, the Indirect Data Map is set up in RMCTools. However, you can change the Indirect Data Map during runtime to map different registers. To do this, write to the Indirect Data Map Definition registers. The Indirect Data Map Definition registers contain the addresses of the mapped registers. When writing addresses to the Indirect Data Map Definition registers, those addresses must be entered as an integer value as described here:

RMC addresses are represented in IEC format as:

%MDfile.element, where file = file number, and element = element number.

Use the following equation to convert a register address to integer format, N:

N =  file * 4096 + element

Example:

Register address %MD8.33 is 8*4096 + 33 = 32801.

See Also

Communications Overview | Indirect Data Map Editor

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