3. Instruction Set
RTU mode (COM3: M1320 = ON, COM1: M1139 = ON):
When X0 = ON, MODRW instruction executes the function specified by Function Code 05
PLC1 PLC2, PLC1 sends: “01 05 0500 FF00 8C F6”
PLC2 PLC1, PLC1 receives: “01 05 0500 FF00 8C F6”
(No data processing on received data)
Program Example 7: COM2(RS-485), Function Code H06
1. Function code K6 (H06): Write in single word device.
2. Set the value to be written into VFD-B in the register specified by operand S.
3. For ASCII or RTU mode, PLC COM2 stores the data to be sent in D1256~D1295, and
received data in D1070~D1085.
4. Take the connection between PLC (PLC COM2) and VFD-B for example, the tables below
explains the status when PLC reads status of VFD-B. (M1143 = OFF, ASCII Mode) (M1143 =
ON, RTU Mode)
H87MOV
M1002
D1120
SET M1120
K100
MOV
D1129
RST M1127
Set communication protocol as 9600, 8, E, 1
Retain communication protocol
Set communication timeout as 100ms
MODRW K6K1
X0
H2000 D50 K1
Connection device
address: K1
Function code K6
write in single data
Data address: H2000
Data storing register
D50=H1770
Data length
Processing received data
ASCII mode: The received data is stored in D1070~D1085 in ASCII format
RTU mode: The received data is stored in D1070~D1085 in Hex format
Reset M1127
M1127
SET
X0
M1122
Sending request
M1143 = OFF
ASCII mode
RST
M1143
M1143 = ON
RTU mode
SET
M1143
Receiving completed
ASCII mode (M1143 = OFF)
When X0 = ON, MODRW instruction executes the function specified by Function Code 06
PLC VFD-B, PLC sends: “01 06 2000 1770 52”
VFD-B PLC, PLC receives: “01 06 2000 1770 52”
Registers for data to be sent (sending messages)
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