Mitsubishi MELSEC System Q Manual page 128

Programming Tips for Timers and Counters
Ladder Diagram
– When relay M15 is on the contents of data register D100 is copied to D31. This register
contains the setpoint value for T31. You could use a programming or control unit to adjust
the contents of D100.
– The special relay SM402 is only set for a single program cycle directly after the PLC is
switched on. This is used to copy the constant value 34 into data register D5, which is then
used as the setpoint value for counter C0.
You don't have to write program instructions to copy the setpoint values to the data registers.
You could also use a programming unit to set them before the program is started, for example.
E
WARNING:
If you use normal registers the setpoint values will be lost when the power supply is
switched off and when the RUN/STOP switch is set to the STOP position. If this happens
hazardous conditions may be created next time the power is switched on and/or when
the PLC is started again, because all the set points will have a value of "0".
If you don't configure your program to copy the values automatically you should always
use latched data registers for storing the setpoint values for timers and counters. Also,
remember that even the contents of these registers will also be lost when the PLC is
switched off if the backup battery is empty.
5 – 16
Devices in Detail
MELSEC Instruction List
LD M15
MOV D100
D31
LD X1
OUT T31
D131
LD SM402
MOV K34
D5
LD M50
OUT C0
D5
IEC Instruction List
LD M15
MOV_M D100, D31
LD X1
TIMER_M TC31, D31
LD SM402
MOV_M K34, D5
LD M50
COUNTER_M CC0, D5
MITSUBISHI ELECTRIC