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9. COMMUNICATIONS IN THE NO-PROTOCOL MODE
MELSEC-A
IREMARKS]
If the receive data length exceeds the no-protocol mode receive buffer memory size, the data
is processed as described below.
(1) When the receive completed code is used:
If the A1 SJ71C24 receives data that exceeds the receive area size, it turns ON the received
data read request signal Xnl when data equivalent to the receive area size has been
received.
Reading the remaining data is enabled at the time the sequence program turns the receive
data read completed signal Y ( n + l ) l ON.
These steps are repeated until the receive completed code is received.
Set
the receive area size
so
that 'receive-completion data length" is less than 'no-protocol
mode receive buffer memory size".
Example: To receive 150 words of data while receive area is set at 80H to FFH (default)
r
Read completed code
External device
Received data read request
Xnl
Received data read completed
Yl"+,ll
A1 SCPU program
(Reads 127 words of data)
(Read 23 words of data)
(2) When receive completion data length is used:
If the receive completion datalength is set greater than
the
receiveareasize, the no-protocol
receive buffer memory size (default: 127 words) which is set at buffer memory address 107H
is taken as the receive completion data length.
Set
the receive area size
so
that 'receive completion data length" is less than 'no-protocol
mode receive buffer memory size'.
Example: To receive 150 words of data while receive
area
is set at 80H
to
FFH (default setting).
Received
data read
request Xnl
Receive
data read
completed
A1 SCPU program
FROM instruction
Y["+lll
(Reads 127 words of data
(Read 23 words of the first
of the first transmission)
transmission, and 104 words of
the second transmission)
Data transmitted for the first time
Data transmitted for the second time
Data transmitted for the third time
device
\
\
81 words
External
69
words
104 words
46
words
127 words
23
words
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