VSCOM NetCom Plus 111, User Manual

Page: 124 / 133

12 Modbus/TCP for Digital-Input/Output
12.2 Examples
12.2.1 Read two input signals
Function Read Coils is native to get the status of input signals. Here we read the status of Input
2 and 3, to see if the two pins of each are connected to each other or not.
Request:
Function Code 01 one byte
Start Address 0001 a 16 bit value (two bytes), 01 refers to Input 2
Quantity 0002 a 16 bit value (two bytes), two values shall be read.
Response:
Function Code 01 one byte, the same as in the request
Byte Count 0001 one byte. The requested data are two bits only, they fit in one
byte
Data Byte 02 one byte as an example. This least significant bit (LSB) states
the Input 2 is open (zero), and Input 3 is closed (One)
In the same way it is possible to read the status of the output signals. Normally your application
would know this status, since it is likely it defined this before the request.
12.2.2 Write one output signal
This example will set the status of Output 8 to 1 (One), to make a connection between the pins
labelled 8 (central) and S.
Request:
Function Code 05 one byte
Output Address 0015 a 16 bit value (two bytes), 07 refers to Output 8
Value FF00 a 16 bit value (two bytes), a special value as opposite to 0000
Response:
Function Code 05 one byte
Output Address 0015 a 16 bit value (two bytes), the same as in the request.
Value FF00 a 16 bit value (two bytes)
In this case the response looks the same as the request.
September 2016 NetCom Plus User Manual 124