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3.
LINKING TO THE A2CCPU
MELSEC-A
(3)
Reading data from the A64RDC buffer
(9
The FROM instruction information is written
to the request-to-com-
municate registration area by the execution of the TO instruction,
and registration of the FROM instruction information is completed by
execution of the PRC instruction.
(9) The PC CPU starts processing instructions of the next and following
steps when the FROM instruction information has been registered.
(The instruction processing will not wait
for a transmission-com-
pleted response.)
The FROM instruction information stored in the communications
request registration area is transmitted in several steps to the
A64RDC. This is done via the word data send area to the A64RDC
after execution of the END instruction.
(h) Upon receiving the FROM instruction information, the A64RDC
transmits data stored in a designated buffer address
back to the
A2CCPU according to the information
it
receives.
(i) The data is transmitted at the rate of one word per communication
from the A64RDC and stored in the storage devices specified by the
FROM instruction.
(j) The communications-completed flag
(M2) designated by the PRC
instruction is turned
ON for one scan from step
0
of the scan
immediately after the storage of read data in designated devices is
completed.
Step
0
END
PRC instruction
execution
-. . - -JJ-5\
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Communications execution
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Communications-completed
flag
1 1
-
Max.
1 scan
1 scan
-4
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3.2.2 Processing time
This section describes the processing time required to read data from and
write data to the buffer area of an A64RDC.
(1)
Processing time required to write data
Max. processing time = 2 scan time
+
10
msec x (number of write data
words
t
7)
t
40 msec *1
(2)
Processing time required to read data
Max. processing time
=
2 scan time
+
10
msec x (number of read data
words
+
8)
+
40 msec
*1
*1: Internal processing time of the A64RDC
3 - 6
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