Rockwell Automation 1769-SM2 Compact I/O DSI/Modbus Communication Module - Manual (Page 99)

MicroLogix 1500 Example Ladder Programs 6-19
The Logic Command/Reference write message instruction on rung 0000
is configured as follows:
Figure 6.7 Example MicroLogix 1500 Modbus RTU Ladder Logic CH3 Subroutine (Continued)
Write Parameter 100 [Jog Frequency] (written 1x per request).
N7:120 = Slave Address ("15" is the 20-COMM-H address)
N7:121 = Function Code ("6" is Write Single Register command)
N7:122 = Starting Address ("1099" = 4x1100)
N7:123 = Length ("1")
N7:124 = Pr. 100 [Jog Frequency] Write Value
0004
B3:30
2
CH3
Write
Pr.100
EN
DN
ER
MSG
Read/Write Message
MSG File MG9:22
Setup Screen
MSG
Read Parameter 100 [Jog Frequency] (read 1x per request).
N7:130 = Slave Address ("15" is the 20-COMM-H address)
N7:131 = Function Code ("3" is Read Holding Register command)
N7:132 = Starting Address ("1099" = 4x1100)
N7:133 = Length ("1")
The response data is stored in:
N7:134 = Pr. 100 [Jog Frequency] Read Value
0005
B3:30
3
CH3
Read
Pr.100
EN
DN
ER
MSG
Read/Write Message
MSG File MG9:23
Setup Screen
MSG
0006
RET
Return
RET
0007 END