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SN54/74LS569A
FOUR-BIT UP/DOWN COUNTER
WITH THREE-STATE OUTPUTS
The SN54 / 74LS569A is designed as programmable up/down BCD and
Binary counters respectively. These devices have 3-state outputs for use in
bus organized systems. With the exception of output enable (OE) and
FOUR-BIT UP / DOWN COUNTER
asynchronous clear (ACLR), all functions occur on the positive edge of the WITH THREE-STATE OUTPUTS
clock pulse (CP).
LOW POWER SCHOTTKY
When the LOAD input is LOW, the outputs will be programmed by the
parallel data inputs (A, B, C, D) on the next clock edge. Enabling of the
counters occurs only when CEP and CET are LOW and LOAD is HIGH.
Direction of the count is controlled by the up-down input (U/D), HIGH counts
up and LOW counts down. High-speed counting and cascading is implement-
ed by internal look-ahead carry logic and an active LOW ripple carry output
J SUFFIX
(RCO). On the LS569A, the RCO is LOW at binary 15 during up-count and
CERAMIC
during down-count it is also LOW at binary 0. During normal cascading CASE 732-03
operation RCO connected to the succeeding block at CET is the only 20
requisite. When counting and when RCO is LOW, the clocked carry output 1
(CCO) provides a HIGH-LOW-HIGH pulse for a duration equal to the LOW
time of the clock pulse. Two active LOW reset lines are provided, a master
N SUFFIX
reset asynchronous clear (ACLR) and a synchronous clear (SCLR). When in
PLASTIC
a HIGH state, the output control (OE) input forces the counter output into a CASE 738-03
HIGH impedance state and when LOW, the counter outputs are enabled. 20