MVI69E-MBS ♦ CompactLogix™ Platform
Reference
Modbus Serial Enhanced Communication Module
User Manual
ProSoft Technology, Inc.
Page 114 of 159
8.2.1 Modbus Master
A port configured as a virtual Modbus Master actively issues Modbus commands to
other nodes on the Modbus network, supporting up to 250 commands on each port. The
Master ports have an optimized polling characteristic that polls slaves with
communication problems less frequently.
Parameter
Description
Command List
Up to 250 commands per Master port, each fully configurable for function,
slave address, register to/from addressing and word/bit count.
Polling of command list
Configurable polling of command list, including continuous and on change
of data, and dynamically user or automatic enabled.
Status Data
Error codes available on an individual command basis. In addition, a slave
status list is maintained per active Modbus Master port.
8.2.2 Modbus Slave
A port configured as a Modbus slave permits a remote Master to interact with all data
contained in the module. This data can be derived from other Modbus slave devices on
the network, through a Master port, or from the CompactLogix or MicroLogix 1500-LRP
processor.
Parameter
Description
Node address
1 to 247 (software selectable)
Status Data
Error codes, counters and port status available per configured slave port
8.2.3 Function Codes Supported by the Module
The format of each command in the list depends on the Modbus Function Code being
executed. The following table lists the Function Codes supported by the MVI69E-MBS
module.
Function Code
Definition
Supported as Master
Supported as Slave
1
Read Coil Status 0x
X
X
2
Read Input Status 1x
X
X
3
Read Holding Registers 4x X
X
4
Read Input Registers 3x
X
X
5
Set Single Coil 0x
X
X
6
Single Register Write 4x
X
X
8
Diagnostics
X
15
Multiple Coil Write 0x
X
X
16
Multiple Register Write 4x
X
X
17
Report Slave ID
X
22
Mask Write 4X
X
23
Read/Write
X
Each command list record has the same general format. The first part of the record
contains the information relating to the communication module and the second part
contains information required to interface to the Modbus slave.