8.
COMMUNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
(3)
Communications time
This section describes how to calculate approximate communications
time from the start of data transmission from the computer to the
completion of all communications after a reply is sent from the
AJ71 C24.
For TO to T4, see
(1)
and (2) on the previous page.
(a) To read data from the PC CPU to the computer
Communications time
=
TO
+
(longer
time
of
T1
+
T2
or
TW)
+
T3
+
T4
where,
TO, T3,T4
=
l/baud rate
X
the number of bits per character
(1
+
7/8
+
0/1
+
1/2
x
the character length
TTT-4
Data length
(7
or
8)
Start bit
Stop bit
(I
or 2)
Parity bit
(0
or
1)
11
=
maximum 1 scan time (since data entry to the PC CPU is made
after
END
processing. If
the
PC CPU is not running, 11 is
0.)
I::
=
value in Appendix
5
=
menage wait time
(b) To write data from the computer
to
the PC CPU
..
~the=TO+(kngertimedTl+T2+T3+TS~~+T4
where,
TO,
T4
T1
lzn
Tw
T5
Start bit
Data length
(7
or
8)
Parity bit
(0
or
1)
Stop bit (1 or
2)
=
maximum
1
scan time (since data entry to the PC CPU is made
after END processing.
If
the PC CPU is not running, T1 is
0.)
=
value in Appendix
5
(For functtons processed in
1
scan,
T3
is
0.)
=
message
wait
time
=
1
scan time
(For functions processed in one
SCM,
T5
is
0.)
8-
17
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