Rockwell Automation 1769-SM2 Compact I/O DSI/Modbus Communication Module - Manual (Page 125)

CompactLogix Example Ladder Programs 7-23
Figure 7.7 Example CompactLogix Modbus RTU Ladder Logic CH3 Subroutine (Continued)
Write Parameter 100 [Jog Frequency] (written 1x per request)
CH3_MSG3_REQ[0] = Slave Address ("15" is the 20-COMM-H address)
CH3_MSG3_REQ[1] = Function Code ("6" is Write Single Register command)
CH3_MSG3_REQ[2] = Starting Address ("1099" = 4x1101)
CH3_MSG3_REQ[3] = Length ("1")
CH3_MSG3_REQ[4] = Pr.100 Write Value
4
Channel 3
Write Pr.100
CH3_WR_Pr100
EN
DN
ER
Type - CIP Generic
Message Control CH3_MSG3 ...
MSG
Read Parameter 100 [Jog Frequency] (written 1x per request)
CH3_MSG4_REQ[0] = Slave Address ("15" is the 20-COMM-H address)
CH3_MSG4_REQ[1] = Function Code ("3" is Read Holding Register command)
CH3_MSG4_REQ[2] = Starting Address ("1099" = 4x1101)
CH3_MSG4_REQ[3] = Length ("1")
The response data is stored in:
CH3_MSG4_RESP[0] = Pr.100 Read Value
5
Channel 3
Read Pr.100
CH3_RD_Pr100
EN
DN
ER
Type - CIP Generic
Message Control CH3_MSG4 ...
MSG
6 Return
RET
(End)