Omron CP1L CPU UNIT - 03-2009, Operation Manual

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High-speed Counters Section 5-1
• Only up-differentiated pulses (rising edges) can be counted.
Note The count of the high-speed counter can be monitored to see if it is currently
being incremented or decremented. The count in the current cycle is com-
pared with the count in the previous cycle to determine if it is being incre-
mented or decremented. The results are reflected in the High-speed Counter
Count Direction Flags (A274.10 for high-speed counter 0, A275.10 for high-
speed Counter 1, A320.10 for high-speed counter 2, and A321.10 for high-
speed counter 3.)
Counting Modes
Linear Mode Input pulses can be counted in the range between the lower limit and upper
limit values. If the pulse count goes beyond the lower/upper limit, an under-
flow/overflow will occur and counting will stop.
Lower and Upper Limits of the Range
The following diagrams show the lower limit and upper limit values for incre-
ment mode and up/down mode.
Circular (Ring) Mode Input pulses are counted in a loop within the set range. The loop operates as
follows:
• If the count is incremented from the max. ring count, the count will be
reset to 0 automatically and incrementing will continue.
• If the count is decremented from 0, the count will be set to the max. ring
count automatically and decrementing will continue.
Consequently, underflows and overflows cannot occur when ring mode is
used.
Max. Ring Count
Use the PLC Setup to set the max. ring count (Circular Max. Count), which is
the max. value of the input pulse counting range. The max. ring count can be
set to any value between 00000001 and FFFFFFFF hex.
4294967295
(FFFFFFFF hex)
−
2147483648
(80000000 hex)
0
(00000000 hex)
+2147483647
(7FFFFFFF hex)
PV overflow
Increment Mode
Up/Down Mode
PV underflow
PV overflow
0
(000000 hex)
2
32
−
1
0
Count value
Max. ring
count