ICP DAS USA tGw-735 - 0 X03) Read the Holding Registers (Readback Aos)

Tiny Modbus/TCP to RTU/ASCII Gateway
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03(0x03) Read the Holding Registers (Readback AOs)
This function code is used to readback either the current values in the holding registers or the
analog output value.
[Request]
Byte
Description
Size
Value
00
Net ID (Station Number)
1 Byte
1 to 247
01
Function Code
1 Byte
0x03
02-03
Starting AO Address
2 Bytes
Refer to the Modbus address depends on your
slave device for more details.
Byte 02 = high byte
Byte 03 = low byte
04-05
Number of 16-bit Registers
(Channels)
2 Bytes
Word Count
Byte 04 = high byte
Byte 05 = low byte
[Response]
Byte
Description
Size
Value
00
Net ID (Station Number)
1 Byte
1 to 247
01
Function Code
1 Byte
0x03
02
Byte Count
1 Byte
Byte Count of the Response
(n=Points x 2 Bytes)
03~
Register Values
n Bytes
Register Values
n= 2; Byte 03 = high byte
Byte 04 = low byte
.......
n= m; Byte 03 = high byte
Byte 04 = low byte
.......
Byte m+1 = high byte
Byte m+2 = low byte
[Error Response]
Byte
Description
Size
Value
00
Net ID (Station Number)
1 Byte
1 to 247
01
Function Code
1 Byte
0x83
02
Exception Code
1 Byte
Refer to the Modbus Standard Specifications for
more details