
B–61863E/15
3. PMC I/O SIGNAL DISPLAY AND
INTERNAL RELAY DISPLAY
(PMCDGN)
PMC OPERATION (CRT/MDI)
463
(b) OVERRIDE mode
That state in which values modified by the forced input/output
function cannot be overwritten by a sequence program or
machine signal is referred to as OVERRIDE mode. In
OVERRIDE mode, OVERRIDE can be set for arbitrary X and Y
signals.
FORCING is applied to those X and Y addresses where
OVERRIDE is not set, and also to addresses other than the X and
Y addresses.
Machine
Overwrite disabled
Ladder
I/O address
X, Y
G, F, R, T, K, C, D. .
Overwrite
(OVERRIDE)
(NOT OVERRIDE)
X, Y
Overwrite disabled
Example:
In this example, the forced input/output function is applied to X0
in a configuration where the I/O UNIT–MODEL A is connected
to X0 with an I/O link.
I/O UNIT–MODEL A NC
X0 = FFH X0 = FFH
OVERRIDE is set for X0.
A value transferred from the I/O
UNIT–MODEL A is invalidated.
I/O UNIT–MODEL A NC
X0 = FFH X0 = FFH
X
I/O UNIT–MODEL A NC
X0 = FFH X0 = 00H
X
Value 00H is forcibly entered to X0.
Thus, the forced input/output function for X addresses in
OVERRIDE mode can be used to debug a sequence program
while a machine is connected.
When a Y address is placed in the OVERRIDE state, a value that
has been forcibly modified by the forced input/output function is
output to the machine.