Modbus Rtu Protocol - ICP DAS USA tM-TH8 User Manual

3. Modbus RTU Protocol

The Modbus protocol is developed by Modicon Inc., originally
developed for Modicon controllers. Detailed information can be
found at http://www.modicon.com/techpubs/toc7.html. You can
also visit http://www.modbus.org
information.
The tM-TH8 supports the Modbus RTU and Modbus ASCII
protocols. The communication Baud Rates range from 1200bps
to 115200bps. The following Modbus functions are supported by
the tM-TH8.
Function Code
01 (0x01)
02 (0x02)
04 (0x04)
05 (0x05)
15 (0x0F)
70 (0x46)
If the function specified in the message is not supported, then the
module responds as follows.
Error Response
00 Address
01 Function code
02 Exception code
If a CRC mismatch occurs, the module will not respond.
108 tM-TH8 User Manual, Rev: A1.1 7MH-018-A11
Description
Read digital output status
Read input status
Read input channels
Write single digital output
Write multiple digital outputs
Read/write module settings
1 Byte 1 to 247
1 Byte Function code | 0x80
1 Byte 01
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Section
3.1
3.2
3.3
3.4
3.5
3.6