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9.
COMMUNICATIONS IN THE NO-PROTOCOL MODE
MELSEC-A
9.2
Handshake I/O Signals
Signals known as I/O handshake signals are required for no-protocol com-
munications.
These signals (a) output data received from the sequence program to an
external device, or (b) detect signals from an external device to enable the
sequence program to read them.
Signal
I
Turned 0N'by program
Timing
PC
CPU
1
External
device
Y I ~ + ~ I O (Send
request)
XnO
(Send
completed)
Turned OFF by program
Turned ON by program
Turned OFF by
AJ71 C24
Turned
ON by AJ71C24
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