FPΣ User's Manual 
 
11.10 No RS232C Communication 
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11.10 No RS232C Communication 
A communication error can be detected when monitoring the special relays for serial 
communication. 
•  Check whether the RD terminal of a connected device is connected to the SD terminal 
of the communication cassette, and that SD is connected to RD. Make sure SG is 
connected. 
•  Check that link areas do not overlap. 
When using FPG-COM1: 
Data cannot be sent unless the pin CS (Clear to Send) is on. When connecting to a three-wire 
port, short-circuit the RS and CS pins. 
•  Check if the CS signal is TRUE. If the LED COM.2 R on the CPU is off, the CS signal 
is FALSE. 
•  RS (Request to Send) can be controlled by the SYS1 instruction.