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MELSEC-
A
6 SEQUENCE PROGRAM USED FOR POSITIONING CONTROL
[5] Reading and writing the D75P2 buffer memory
This section explains the method of reading and writing the D75P2 buffer memory
using transient transmission.
(1) Outline
When reading and writing the D75P2 buffer memory, reading and writing are
carried out using the intelligent device station access request signal (RY(n+7)E)
and the intelligent device station access complete signal (RX(n+7)E).
The master module buffer memory uses the transmission/reception buffer.
TO (RIWT)
FROM (RIRD)
1) 2)
3)4)
PLC CPU Master module
D75P2 (1st station)
Buffer memory
Reception area
2nd station transmission/
reception area
Buffer memory
(Transmission/reception area)
Transmission area
...
1st station transmission/reception area
1) Data (control data + transmission data) is stored in the master module
transmission area.
2) When the intelligent device station access request signal (RY(n+7)E) turns
ON, the data stored in the transmission area is stored in the D75P2.
3) When the intelligent device station access complete signal (RX(n+7)E) turns
ON, the response is stored in the master module reception area.
4) The data (control data + reception data) is read from the master module
reception area.
POINT
When the dedicated commands RIWT/RIRD are used, the intelligent device station
access request signal (RY(n+7)E) and intelligent device station access complete
signal (RX(n+7)E) are controlled by the dedicated commands, so the user does not
need to establish an interlock.
(a) Changing the bank
The master station's automatic transmission/reception buffer will be "bank
1".
Thus, create a program that changes to "bank 1"when reading or writing to
the transmission/reception buffer, and returns to "bank 0" when the
reading/writing is completed.
When using the dedicated commands RIWT/RIRD, the bank will be
changed automatically by the dedicated commands, so the user does not
need to change the bank.
Refer to section [2] for details on changing the bank.