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NO
NO
YES
NO
YES
Start
Is power
LED lit?
Is M8063
turned on?
• Check connection with the PC.
• Check power source of PC.
• There is a possibility of send crosstalk. Check the send and receive
timing with the external RS232C device.
• The receive data length may exceed the receive data area.
Check the receive data length and timing of receive start.
• Check that the program is not set so that M8122 may be always on .
• Match the communication format.
• Check the wiring of control line.
• Check the start timing of send, receive.
No send
or receive
error
The data
transfer
complates
once.
No send or receive error
Only receiving
fails to operate
normally
Is send
wait flag M8121
turned on?
Is SD LED
(send) lit up
momentarily?
Is the send
data remainder
zero?
• Check wiring of RS232C cable.
• Check wiring of control line.
• Make sure the receiving external device is normal.
• Check the voltage level of RS232C signal (±9 V).
• Make sure content of send data and communication format
are established before driving RS instruction.
• Check the timing of control line.
• Check the wiring of RS232C cable.
• Check the wiring of control line.
• Match the communication format.
• Make sure the receiving external device is normal.
(CR, LF may be needed in some printers.)
• Check the data format of sending device.
Send,
receive
error
YES
NO
YES
NO
1
YES
YES
NO
NO
YES
• Check wiring of control line.
• Check timing of send, receive.
• Change RS instruction from OFF to ON.
• Make sure the received data length matches with the receive
data area length.