User manual

IEC61131 User and Reference Manual
April 22, 2008
399
Report Slave ID
The Report Slave ID function reads a variable length message containing controller specific
information. The information and the length of the message is defined by the application
program. This function is included for compatibility with devices expecting to communicate
with a Modicon PLC.
Modbus Master Mode
The TeleBUS protocol may act as a communication master on any serial port. In master
mode, the controller sends commands to other devices on the network. Simultaneous
master messages may be active on all ports.
The protocol cannot support master mode and store-and-forward mode simultaneously on a
serial port. Enabling store and forward messaging disables processing of responses to
master mode commands. Master mode may be used on one port and store-and-forward
mode on another port.
Modbus Function Codes
The table shows the implemented function codes. The maximum number of registers that
can be read or written with one message is shown in the maximum column. The slave
device may support fewer registers than shown; consult the manual for the device for details.
Function
Name
Description
Maximum
01
Read Coil Status
Reads digital output registers.
2000
02
Read Input Status
Reads digital input registers.
2000
03
Read Holding Register
Reads analog output registers.
125
04
Read Input Register
Reads analog input registers.
125
05
Force Single Coil
Writes digital output register.
1
06
Preset Single Register
Writes analog output registers.
1
15
Force Multiple Coils
Writes digital output registers.
880
16
Preset Multiple
Registers
Writes analog output registers.
60