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Timers in interlocked program sections are reset when the execution condi-
tion for IL(02) is OFF. Power interruptions also reset timers. If a timer that is
not reset under these conditions is desired, SR area clock pulse bits can be
counted to produce timers using CNT. Refer to
5-11-4 COUNTER – CNT
for
details.
Program execution will continue even if a non-BCD SV is used, but timing will
not be accurate.
ER: SV is not in BCD.
5-11-3 Analog Timer Unit
The Analog Timer Unit uses two I/O words to provide four timers (T
0
to T
3
).
Each of the four timers may be set to a specific timer value (SV) within one of
four ranges. The SV for each timer may be set using either a variable resistor
on the Analog Timer Unit or from an external variable resistor.
Each timer is allocated five bits within the IR words allocated to the Analog
Timer Units. The function of these is shown below. The words shown in the
table are as seen from the CPU, i.e., the input word goes from the Analog
Timer Unit to the CPU, the output word, from the CPU to the Analog Timer
Unit. The CPU receives the Time Expired flag from the Unit and sends the
Start control bit Pause control bit and Range bits to the Unit.
Bit Input word Output word
00 T
0
Time Expired flag T
0
Start control bit
01 T
1
Time Expired flag T
1
Start control bit
02 T
2
Time Expired flag T
2
Start control bit
03 T
3
Time Expired flag T
3
Start control bit
04 T
0
Pause control bit
05
T
1
Pause control bit
06 T
2
Pause control bit
07 T
3
Pause control bit
08 T
0
Range bits
09 Cannot be used.
10 T
1
Range bits
11
12 T
2
Range bits
13
14 T
3
Range bits
15
There is a SET indicator and a time expired indicator on the Analog Timer
Unit for each timer. These indicators are lit when the corresponding timer’s
Start control bit or Time Expired flag is ON.
When the Start control bit is turned ON, the timer begins operation and the
SET indicator is lit.
When the time set with the internal or external adjustment has expired, the
corresponding Time Expired flag is set. The time up indicator also lights.
If the Pause control bit for a timer is turned ON from the PC, the timer will
cease timing and the present value (PV) will be retained. Timing will resume
when the Pause control bit is turned OFF. If the Start control bit is turned
OFF before the set value (SV) of the timer has expired, the Time Expired flag
will not be turned ON.
Precautions
Flags
Timer and Counter Instructions Section 5-11