Function Block Diagram - Mitsubishi MELSEC-A AJ71PT3 User Manual

1. INTRODUCTION
_ _ _ _ _ _ _ _ _ _--..;/MELSEC;4
1.2 Function Block Diagram
Fig. 1.2 shows the sequence of remote I/O station data in the MINI
link.
(1) I/O refresh is continuously executed between the master
module and remote I/O stations at intervals of 3.2 to 3.9ms
(512 points).
(2) I/O refresh and master station sequence program are executed
asynchronously, with the exception that I/O refresh is stopped
while the
I
FROM
[jQJ
instruction is executed from the PC
CPU to the master module.
•
(3) Input data from a remote I/O station is read from the master
module buffer memory by the
I
FROM
I
instruction .
(4) Output data to a remote I/O station is written to the master
module buffer memory by the
I
TO
I
instruction.
Master module Remote 1/0 station
•
CD
r -
r -
r -
r -
r -
Master module
~~
1/0 signals
m
@
m
U
u Input
oj ! !
u
m
•
•
n,
Optical/twisted
oj!!
m
u
oS
s
u 's
OJ
air data link
m
oj ! !
m
c,
®
.~
.s
,'g
"0
U
<=>
s
Buffer memory
s
~
~
C
"
U
c
~
c
c,
data transfer
oj!!
~
Output
~
<:
:>
s
s
s
x
rn
E "
rn
w
memory
c
-
-
'-----
'-----
-
-
•
Fig. 1.2 Function Block Diagram
1) I/O signals assigned to the master module. These signals are
used for communication between the
PC CPU
and master
module. For more information, see Section 3.3.
2) Allows remote I/O station input data to be read, output data to
be written, a faulty station to be read, etc. Buffer memory data
transfer is made by the
I
FROM
I
and
I
TO
I
instructions in the
sequence program. For full information of the buffer memory,
see Section 3.4.
3) Data link start is directed from the sequence program. After
data transfer is initiated, I/O refresh is continually executed
independently of the sequence program execution.
1-4
IS (NAI 66164-A