PLC
Destination
(Field device)
1
Frame ground FG
2 Send data SD →
3 Received data RD ←
4 Request to send (always on) RS →
5 Clear to send CS ←
6
Not used −
7
Signal ground terminal SG
8
Not used −
9 Equipment ready (always on) ER →
Note
The serial data communication control instruction (F144) cannot
be executed unless pin 5 is turned on.
Communications specifications
Electrical characteristics conform to EIA RS232C.
The transmission speed and transmission format are decided using the operation con-
dition switches on the CPU.
The table below shows the settings in the default state.
Item Description
Baud rate 9,600bps
Data bit length 8 bits
Parity check Odd parity
Start bit length 1 bit
Stop bit length 1 bit
Starting code for general-
purpose communications
STX invalid
Ending code for general-
purpose communications
CR
The starting and ending codes when using a computer link are determined by the MEW-
TOCOL−COM.
When using the general−purpose communication function (serial data communication
control instruction “F144”), the setting of system register 412 should be changed.
The serial data communication control instruction can be used to switch between the
computer link function and the general−purpose communication function.
If the transmission speed is 38,400 bps or higher, the transmission distance over which
communication is possible is limited to within 3m/9.84ft.
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