3. Instruction Set
3-333
3. In ASCII or RTU mode, when PLC’s COM2 sends out data, the data will be stored in
D1256~D1295. The feedback data will be stored in registers starting with S and converted into
D1296~D1311 in Hex automatically.
4. Take the connection between PLC1 (PLC COM2) and PLC2(PLC COM1) for example, the
tables below explains the status when PLC1 reads Y0~Y17 of PLC2.
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 K2
K1
X0 H0500 D0 K16
Connection device
address K1
Function code K2
read multiple bits
Data address Y0=H0500
Data storing register
Data length (bit)
Processing received data
ASCII mode: The received data is st ore d in reg is t er s st ar tin g fro m D 0 in A S C II fo r ma t an d
PLC converts the content to hexadecimal automatically.registers D1296~D1311 in
RTU mode: The received data is stored in registers starting from D0 in Hex.
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 02.
PLC1Ö PLC2，PLC1 sends: “01 02 0500 0010 E8”
PLC2 ÖPLC1，PLC1 receives: “01 02 02 3412 B5”
Registers for data to be sent (sending messages)
Register Data Descriptions
D1256 Low ‘0’ 30 H ADR 1
D1256 High ‘1’ 31 H ADR 0 Device address: ADR (1,0)
D1257 Low ‘0’ 30 H CMD 1
D1257 High ‘2’ 32 H CMD 0 Control parameter: CMD (1,0)
D1258 Low ‘0’ 30 H
D1258 High ‘5’ 35 H
D1259 Low ‘0’ 30 H
D1259 High ‘0’ 30 H
Y0 = H0500
Starting Data Address