CD54HC190 Datasheet, PDF (2/26 Pages) Texas Instruments – SYNCHRONOUS UP/DOWN COUNTERS WITH DOWN/UP MODE CONTROL

CD54HC190, CD74HC190
CD54HC191, CD74HC191, CD54HCT191, CD74HCT191
SYNCHRONOUS UP/DOWN COUNTERS WITH DOWN/UP MODE CONTROL
SCHS275E − MARCH 2002 − REVISED OCTOBER 2003
description/ordering information (continued)
When an overflow or underflow of the counter occurs, the MAX/MIN output, which is low during counting, goes
high and remains high for one clock cycle. This output can be used for look-ahead carry in high-speed cascading
(see Figure 1). The MAX/MIN output also initiates the ripple clock (RCO) output, which normally is high, goes
low, and remains low for the low-level portion of the clock pulse. These counters can be cascaded using RCO
(see Figure 2).
If a decade counter is preset to an illegal state or assumes an illegal state when power is applied, it returns to
the normal sequence in one or two counts, as shown in the state diagrams (see Figure 3).
LOAD
FUNCTION TABLE
INPUTS
CTEN
D/U
CLK
FUNCTION
H
L
L
Count up
H
L
H
Count down
L
X
X
H
H
X
X
Asynchronous preset
X
No change
D/U or CTEN should be changed only when clock is high.
X = Don’t care
Low-to-high clock transition
2
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