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High-speed Counters Section 5-2
Up/Down Mode The up/down mode uses two signals, an increment pulse input and a decre-
ment pulse input.
Conditions for Incrementing/Decrementing the Count
• The count is incremented for each increment pulse input and decre-
mented for each decrement pulse input.
• Only up-differentiated pulses (rising edges) can be counted.
Increment Mode The increment mode counts single-phase pulse signal inputs. This mode only
increments the count.
Conditions for Incrementing/Decrementing the Count
• 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.
22 1 1 0 0 7 6876 55 44 33
Increment pulse
Decrement pulse
Decrement
pulse
Increment
pulse
Count value
↑ LDecrement
H ↑ Increment
↓ H No change
L ↓ No change
L ↑ Increment
↑ HDecrement
H ↓ No change
↓ L No change
142 151 16
0 9 10876 115 124 133
Pulse
Pulse Count value
↑ Increment
H No change
↓ No change
L No change
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