Suntex TC-7310-RS-M, Operation Manual, Page: 56 / 60

9.3 Modbus Description Example (e.g.: function code 03H)
The following description uses MLSS reading 0035H as an example. If the MLSS is 25
mg/l, confirm that the host and sub-machine communication format settings are correct.
The host sends request commands according to the left column of the table below, then
receives a corresponding response from the sub-machine according to the right column.
This example shows the function code 03H as transmission data format; for other
function codes, the same logic applies.
ASCII Mode:
Request Response
Message Framing Hex Message Framing Hex
ID, Address 01 ID, Address 01
Function code 03 Function code 03
Starting Address Hi 00 Byte Count 04
Starting Address Lo 35 Register value Hi 00
No. of Registers Hi 00 Register value Lo 00
No. of Registers Lo 02 Register value Hi 41
LRC C5 Register value Lo C8
LRC 56
RTU Mode:
Request Response
Message Framing Hex Message Framing Hex
ID, Address 01 ID, Address 01
Function code 03 Function code 03
Starting Address Hi 00 Byte Count 04
Starting Address Lo 35 Register value Hi 00
No. of Registers Hi 00 Register value Lo 00
No. of Registers Lo 02 Register value Hi 41
CRC Check Lo 0D Register value Lo C8
CRC Check Hi 45 CRC Check Lo 65
CRC Check Hi 5A
Note: FLOAT is a 32-bit IEEE 754 format. The above table is divided into two 16-bit
register data transfers. The back 16-bit register (00 00) is transferred first, followed
by the front 16-bit register (41 C8). Every 16-bit format is high-bit in the front and
low-bit in the post. For example, if the MLSS reading is now 25 mg/l, the 16-bit of
FLOAT data (hexadecimal) is 41 C8 00 00. However, the transmission order will be
00 00 41 C8.
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