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10. COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
10.2 Handshake Signals and Buffer Memory
(1)
Handshake signals in the bidirectional mode
Signals known as
I 1 0
handshake signals are required for cornmunica-
tions in the bidirectional mode.
These signals output data received from the sequence program to a
computer or detect signals from an external device to enable the se-
quence program to read them.
AlSCPU
1
Computer
Computer
1
A1 SCPU
-
Signal
Y
1 ~ 1 )
o
(Send
request)
X n O
(Send
completed)
X n l
(Received
data read
request)
Y
I W ~ I I
(Receive
data read
complete)
Timing
I
Turned OFF by program
T"t"ed ON by program
TurnedOFF by AlSJ7lC24
Turned
ON by AlSJ7iC24
TurnedOFF by AiSJ71C24
Turned ON by AlSJ71C24
Turned ON by program
The number 'n" appended to X and Y is determined according to the
position where the A1SJ71C24 is loaded and the number of I10 modules
loaded prior to this module. If this module (A1 SJ71 C24) is loaded at slot
0 in a base module, XnO is expressed as "XO".
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