Programming .01Second Timers
Appendix C
C3
Figure C.1
Timing Diagram
1
0
1
0
1
0
Internal
Clock
Pulses
Enabled
Bit 17
Timed
Bit 15
Begin Timing
T = 3
2 < T < 3
One unit of time base
Example: [TON], Preset = 003; any time base
Note, too, that these timing accuracies refer only to internal
Mini-Processor operation. That is, these intervals refer to the length of time
which occurs between the moment that a timer is initialized (bit 17 set)
and the moment that the timed interval is complete (bit 15 set). Other
factors add to this timer inaccuracy. Chief among these are the response
time of the actual hardware devices controlled and monitored by the
Mini-Processor controller. (Refer to the section concerning Hardware and
Mini-Processor considerations, later on.)
You are urged not to overspecify timing accuracy. In many applications,
timing within 0.1 second will provide accuracy comparable to, or better
than, typical electromechanical timing relays. In general, you may apply
these rules:
for delays of 99 to 999 seconds, use the 1.0-second time base
for delays of 2.00 to 99.9 seconds, use a 0.1-second time base
for delays of 0.02 to 2.00 seconds, use the 10-msec time base
As an observation: when time delays are incorporated in a program to
provide a warmup or initializing period, or to prevent the simultaneous
application of power to high-current devices, inaccuracies on the order
of 50 to 250-msec are probably insignificant. For these uses, the 1.0- or
0.1-second time bases are more than adequate. Applications for the
10-msec timer are discussed on the next page.
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