3. Instruction Set
3-257
Program Example 5: COM1 RS-232
1. Only 8-bit mode is supported. Communication format and speed are specified by lower 8 bits of
D1036.
2. STX/ETX setting function (M1126/M1130/D1124~D1126) is not supported.
3. High byte of 16-bit data is not supported. Only low byte is valid for data communication.
4. Write the data to be transmitted in advance into registers starting from D100 and set M1312
(COM1 sending request) as ON
5. When X0 = ON, RS instruction executes and PLC is ready for communication. D100 will then
start to send out 4 data continuously. When data sending is over, M1312 will be automatically
reset. (DO NOT apply RST M1312 in program). After approximate 1ms, PLC will start to receive
7 data and store the data in 7 consecutive registers starting from D120.
6. When data receiving is completed, M1314 will automatically be ON. When data processing on
the received data is completed, M1314 has to be reset (OFF) and the PLC will be ready for
communication again. However, DO NOT continuously execute RST M1314, i.e. it is suggested
to connect the RST M1314 instruction after the drive contact M1314
Receiving completed and flag reset
Setting communication protocol as 9600,8,E,1
Retain communication protocol
Set up communication time out as 100ms
M1002
MOV H87 D1036
SET M1138
MOV K100 D1249
X0
RS
D100
K4
D120
K7
M1314
Processing received data
RST M1314
Pulse for
sending request
Pulse
Write transmitting data in advance
Sending request
SET
M1312
Sending data: (PLC→External equipment)
D100L D101L D102L D103L
Source data register, starting from
lower 8 bits of D100
Length = 4
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