User manual

IEC61131 User and Reference Manual
April 22, 2008
318
Inputs
Type
Description
SlaveStn
Integer
Modbus station address of the slave station.
Valid range is 0 to 255 if standard addressing is
used, and 0 to 65534 if extended addressing is
used.
SAddress
Integer
Modbus slave register address. The first register
where data will be read from or written to in the
slave controller.
MAddress
Integer
Modbus master register address. The first register
where data will be written to or read from in this, the
master controller. The register type does not have to
match the type of the slave register address. It is
possible to store input registers from a slave into
output registers on the master and vice-versa.
Length
Integer
The length input specifies how many registers are to
be transferred. The maximum length for each
function code is shown in the table below.
TimeOut
Integer
Time-out is maximum time the function block waits
for a valid response from the slave station, in tenths
of seconds. Valid values are 0 to 65535.
Outputs
Type
Description
Done
Boolean
TRUE when the sendCmd input is TRUE and a valid
response has been received from the slave.
FALSE in all other cases.
Error
Boolean
TRUE when the sendCmd input is TRUE and an
error occurs. See the statusMasterCmd for a list of
possible error codes.
FALSE in all other cases.
statusMasterCmd
Integer
The master command status code. See the Master
Command Status Codes table below for description
of each status code.
Modbus Function Codes
Function
Code
Purpose
Description
Maximum
Registers
01
Read Coil Status
Read digital output registers.
2000
02
Read Input Status
Read digital input registers.
2000
03
Read Holding Register
Read analog output registers.
125*
04
Read Input Register
Read analog input registers.
125*
05
Write Single Coil
Write digital output register.
1
06
Write Single Holding
Register
Write analog output registers.
1
15
Write Multiple Coils
Write digital output registers.
880