User manual

IEC61131 User and Reference Manual
April 22, 2008
389
The TeleBUS protocols emulate the Modbus protocol functions required for communication
with a host device. These functions are described below. It also implements functions for
programming and remote diagnostics. These functions are not required for host
communication, so are not described here.
A technical specification for the TeleBUS protocol is available from Control Microsystems. It
describes all the functions in detail. In most cases knowledge of the actual commands is not
required.
Broadcast Messages
A broadcast message is sent to all devices on a network. Each device executes the
command. No device responds to a broadcast command. The device sending the command
must query each device to determine if the command was received and processed.
Broadcast messages are supported for some function codes that write information.
A broadcast message is sent to station number 0.
Function Codes
The table summarizes the implemented function codes. The maximum number of registers
that can be read or written with one message is shown in the maximum column.
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
07
Read Exception
Status
Reads special information.
N/A
15
Force Multiple Coils
Writes digital output registers.
880
16
Preset Multiple
Registers
Writes analog output registers.
60
17
Report Slave ID
Reads controller type
information
N/A
Functions 5, 6, 15, and 16 support broadcast messages. The functions are described in
detail below.