ProSoft Technology PTQ-AFC - Manual (Page 78)

Quick Start PTQ-AFC ♦ Modicon Quantum Platform
User Manual Liquid and Gas Flow Computer for Hydrocarbon Products
Page 78 of 259 ProSoft Technology, Inc.
June 23, 2011
6.8 Modbus Database
The module supports two individual Modbus slaves (Primary and Virtual) to
optimize the polling of data from the remote SCADA system, or from the
processor (through the backplane). Refer to the Modbus Dictionary dialog box in
AFC Manager for information about Modbus addressing.
6.8.1 AFC Modbus Address Space
Addressable Modbus registers are divided into four banks as shown in the
following table.
MODBUS Address Space Allocation: Total Modbus Registers: 131,072
Primary Slave Banks
(131072 registers) Virtual Slave Banks
(20,000 registers)
Holding Registers Input Registers Holding Registers Input Registers
From: 0 From: 0 From: 0 From: 0
To: 65535 To: 65535 To: 9999 To: 9999
The first 100 registers of the virtual slave (registers 0 through 99) are predefined
to map to the first 100 registers of the primary slave. This mapping cannot be
changed. Also, the Virtual Slave Input Registers can be accessed as Virtual
Slave Holding Registers by adding 10000 to the Modbus register address; for
example, Input Register 2386 is the same as Holding Register 12386.
Accessing the Data
The AFC Manager provides an easy way to read and write data from both slaves
through the Modbus Master Interface.