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Programming and operating the FM 352-5
6.10 Operations in the FM 352-5 Library
6.10.7
Down counter (CTD16)
Description
You can count down with "CTD16" (FB122). The counter is decremented by 1 on a rising
edge at the CD input. If the count value reaches the lower limit of -32768, it is no longer
decremented. Any subsequent rising edge at the CD input no longer has an effect.
Signal state 1 at the LOAD input sets the counter to the preset value PV regardless of the
value currently at the CD input.
The Q output indicates whether the current counted value is less than or equal to 0.
Table 6- 54
Down counter (CTD16)
LAD representation
CTD16
EN
ENO
CD
Q
Load
PV
Parameter
Data type
Addresses
Description
CD
BOOL
Input
Counter input.
Load
BOOL
Input
Load input. LOAD input is dominant
over CD.
PV
INT
Input, constant
Preset value. The counter is preset
to PV when the signal level at the
LOAD input is 1.
Q
BOOL
Output
Status of the counter: Q has the
following value:
CV
CV
INT
Output

1 if CV ≤ 0

0 in all other situations
Current count value (possible value:
-32768 to +32767).
FM 352-5 high-speed Boolean processor
Operating Manual, 05/2011, A5E00131318-04
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