VM600 networking manual MAVM600-NET/E 9 - 1
Edition 9 - February 2018
Introduction
SETTING UP A MODBUS CONNECTION (CPUM SW VERSION 071 OR LATER)
9 SETTING UP A MODBUS CONNECTION
(CPUM FIRMWARE VERSION 071 OR LATER)
9.1 Introduction
This chapter describes the implementation of the Modbus software interface for VM600 racks
as used by CPUM cards running firmware version 071 or later. This is the latest
implementation of the Modbus software interface for the VM600 and includes extra registers
to allow more information to be read using Modbus.
All Modbus registers are available for CPUM cards running firmware version 071 or later. It
is also backwards compatible with the existing Modbus server for CPUM cards running
firmware version 067 or earlier.
NOTE: Even if you are using the latest Modbus software interface (for CPUM cards
running firmware version 071 or later), you should also read all of 8 Setting up a
Modbus connection (CPUM firmware version 067 or earlier).
The information given in this chapter is in addition to the information already given
for CPUM cards running firmware version 067 or earlier.
In practice, the improved Modbus server is much more flexible. Extensions have been added
to the Modbus registers so that additional data can be provided by the VM600 system. This
extra data includes:
• Basic and advanced functions for the MPC4
• Board level status information for the MPC4
• Board level status information for the AMC8.
However, the Modbus function codes 01 (Read coil status) and 02 (Read input status) used
for reading discrete (individual one-bit) inputs have not changed.
See Appendix A: MPC4 Modbus register definitions for detailed MPC4 Modbus register
mapping information and Appendix B: AMC8 Modbus register definitions for detailed AMC8
Modbus register mapping information.
9.1.1 Modbus functions supported by the VM600 (version 071 or later)
In addition to the existing Modbus functions (see 8.4.3 Modbus functions supported by the
VM600), CPUM cards running firmware version 071 or later provide the additional Modbus
functions shown in Table 9-1.
Table 9-1: Additional Modbus functions supported
Modbus
function code
Function description
05 (0x05) Write single coil
06 (0x06) Write single register
15 (0x0F) Write multiple coils
16 (0x10) Write multiple registers
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