M54HC423F1R 데이터 시트보기 (PDF) - STMicroelectronics
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M54HC423F1R Datasheet PDF : 14 Pages
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M54/M74HC423/423A
FUNCTIONAL DESCRIPTION (continued)
RE-TRIGGERED OPERATION
When a second trigger pulse follows the first its
effect will depend on the state of the multivibrator. If
the capacitor Cx is being charged the voltage level
of R/C external falls to Vrefl again and Q remains
high i.e. the retrigger pulse arrives in a time shorter
than the period Rx ⋅ Cx seconds, the capacitor
charging time constant. If the second trigger pulse
is very close to the initial trigger pulse it is ineffective
; i.e. the second trigger must arrive in the capacitor
discharge cycle to be ineffective; Hence the
minimum time for a second trigger to be effective
depends on VCC and Cx.
RESET OPERATION
CL is normally high. If CL is low, the trigger is not
effective because Q output goes low and trigger
control flip-flop is reset.
Also transistor Op is turned on and Cx is charged
quicky to VCC. This means if CL input goes low, the
IC becomes waiting state both in operating and non
operating state.
TRUTH TABLE
INPUTS
A
B
CL
H
H
X
L
H
H
X
H
L
H
X
X
L
X: Don’t Care Z: High Impedance
OUTPUTS
Q
Q
L
H
L
H
L
H
NOTE
OUTPUT ENABLE
INHIBIT
INHIBIT
OUTPUT ENABLE
INHIBIT
INPUT AND OUTPUT EQUIVALENT CIRCUIT
4/14
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