Cautions On Fixed-Scan Clocks And Fixed Scan Execution Type Programs - Mitsubishi Q12PRHCPU User Manual

7
PROGRAMMING CAUTIONS
7.2 Cautions on Fixed-Scan Clocks and Fixed Scan Execution Type
Programs
(1) Fixed-scan Clocks (SM409 to SM415)
When system switching occurs, fixed-scan clock measurement is suspended until
system switching is complete.
When system switching is complete, the new control system CPU module starts all
fixed-scan clocks from OFF.
Therefore, the OFF time is extended (T+t') as shown in Diagram 7.6.
The maximum value of the extension time when t=t' is (T+t).
New standby system
New control system
(2) Fixed-scan Clocks (SM420 to SM424)
When system switching is complete, SM420 to SM424 remain OFF in the new control
system CPU module.
Execute the DUTY instruction in the new control system CPU module to make SM420
to SM424 usable in the new control system CPU module.
[Example]
A program starting an SM420 timing clock (1 scan: ON, 3 scan: OFF) by executing the
DUTY instruction in the new control system CPU module.

7.2 Cautions on Fixed-Scan Clocks and Fixed Scan Execution Type Programs

Control system
Control system
Fixed Cycle Clock
OFF
(SM409 to SM415)
Standby system
Fixed Cycle Clock
(SM409 to SM415)
Standby system
Diagram 7.6 Operations of Fixed-scan Clocks at System Switching
SM1518
0
Diagram 7.7 Program That Executes Fixed-scan Clock (SM420) after System Switching
* 1 : This is the contact point for 1 scan: ON in the new control system after SM1518 system
switching.
If DUTY instructions are executed for SM1518 shutdown, the DUTY instructions are executed
on the second scan following system switching.
New standby system
System switching activated
ON
Non - executed
t t t'
System Switching complete
Begin system switching
OFF
T t'
Extension of
Off time
New control system
DUTY K1 K3
ON
t
(t-t')
t : ? x fixed cycle interval
T : System switching time
t' : period between start of fixed
cycle clock OFF and beginning
of system switching (0 t' t)
Perform DUTY
instruction during
SM420
SM1518 shutdown.
1
2
3
4
5
6
7
*1
8
7
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