General Measure GM8802F-2 User Manual page 15

MODBUS-ASCII
GM-SP1
DATA4 —— 1bit，high and low byte mode by MODBUS protocol：30H：high byte in the
front；31H：low byte in the front. But for GM-SP1 protocol，both of 30H and
31H are available
O —— 1 bit，4FH
K —— 1 bit，4BH
CRC —— 2 bit，
CRC calculate：Add all of front digits and convert to decimal system, then take the last two
digits to convert to ASCII（tens digit in the front and unit's digit at back）.
For example：
Case 1：Define address 01 parameters：baud rate 38400、ModbusASCII、data format
7-E-1、high byte in the front.
Command：02 30 31 55 53 45 54 32 31 30 30 31 35 0D 0A
Response:02 30 31 55 53 45 54 4F 4B 37 34 0D 0A
Case 2： Define address 01 parameters： baud rate 57600、 Modbus RTU、 data format 8-E-1、
low byte in the front.
Command：02 30 31 55 53 45 54 33 30 30 31 31 36 0D 0A
Response: 02 30 31 55 53 45 54 4F 4B 37 34 0D 0A
Case 3：Define address 01 parameters：baud rate 9600、GM-SP1、data format 7-O-1。
Command：02 30 31 55 53 45 54 30 32 31 30 31 35 0D 0A
Response: 02 30 31 55 53 45 54 4F 4B 37 34 0D 0A
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Checksum
GM8802F-2 Field Mounting Transmitter
30H
31H
32H
33H
30H
31H
32H
33H
7-E-1
7-O-1
7-N-2
Reserve
7-E-1
7-O-1
7-N-2
8-N-1
GM8802-F2110101