Mitsubishi Q12PRHCPU - 7.2 Cautions on Fixed-Scan Clocks and Fixed Scan Execution Type Programs

7
PROGRAMMING CAUTIONS
7.2 Cautions on Fixed-Scan Clocks and Fixed Scan Execution Type Programs
7 - 9
1
OVERVIEW
2
SYSTEM CONFIGURATION
3
TRACKING CABLE
4
PROCEDURE FOR STARTING UP A REDUNDANT SYSTEM
5
REDUNDANT SYSTEM FUNCTIONS
6
REDUNDANT SYSTEM NETWORKS
7
PROGRAMMING CAUTIONS
8
TROUBLESHOOTING
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).
(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.
* 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.
Diagram 7.6 Operations of Fixed-scan Clocks at System Switching
Diagram 7.7 Program That Executes Fixed-scan Clock (SM420) after System Switching
t' : period between start of fixed
cycle clock OFF and beginning
of system switching (0 t' t)
OFF
ON
Fixed Cycle Clock
(SM409 to SM415)
Fixed Cycle Clock
(SM409 to SM415)
tt
Begin system switching
OFF
(t-t')
ON
t
T
Extension of
Off time
System Switching complete
t : ? x fixed cycle interval
T : System switching time
System switching activated
t'
t'
Control system
Control system
New standby system
New control systemStandby system
New standby system
Non - executed
Standby system
New control system
Perform DUTY
instruction during
SM1518 shutdown.
*1
SM1518
0
DUTY K1 K3 SM420