ProSoft Technology MVI56-AFC - Manual (Page 245)

MVI56-AFC ♦ ControlLogix Platform MVI56-AFC Sample Logic
Liquid and Gas Flow Computer User Manual
ProSoft Technology, Inc. Page 245 of 316
February 25, 2011
12.3.15 Modbus Gateway
The ladder logic can be used to read or write data from one of the internal
Modbus Slaves (primary or virtual). Also, any data that is not part of the
AFC56.Meters[ ].Results must be read through the Modbus Gateway blocks.
Each block can transfer up to 200 words of data and uses a specific
AFC56.Modbus.Gateway[ ] controller tag. Each one of these tags must be
configurable in order to read or write data between the module and the
processor.
Perform the following steps to use the Modbus Gateway blocks:
1 Identify how many words (total) will be transferred. The sample ladder
supports up to 2000 words.
2 Based on the number of registers to be transferred, calculate how many
Modbus Gateway blocks will be necessary. Each block contains up to 200
registers. For example: if 700 registers will be used to transfer data, 4
Modbus Gateway blocks will be required.
3 Based on the number of Modbus Gateway blocks, configure the
AFC56.ModbusGateway.CommandCount controller tag.
For example, if you configure the number of blocks as 4, the ladder logic
automatically sends the following Modbus Gateway blocks to the module:
AFC56.ModbusGateway.Command[0]
AFC56.ModbusGateway.Command [1]
AFC56.ModbusGateway.Command [2]
AFC56.ModbusGateway.Command [3]
The maximum number of supported commands by the sample ladder is 10.
If the AFC56.ModbusGateway.CommandCount controller tag is configured as 0
the module will not send any Modbus Gateway blocks.
1 Refer to the Modbus Dictionary dialog box in AFC Manager and identify the
addresses of all registers in the Primary Slave.
2 Using the AFC Manager, re-map the registers from the Primary Slave to the
Virtual Slave (refer to AFC Manager User Manual for more information about
this subject).
3 You must also set a Virtual Slave Address greater than 0 in order to activate
the Virtual Slave.