آي سي 74569 (عداد متزامن 4-بت تصاعدي/تنازلي)

The SN74ALS568A decade counter and
4ALS569A binary counters are programmable,
count up or down, and offer both synchronous and
asynchronous clearing. All synchronous functions
are executed on the positive-going edge of the
clock (CLK) input.
The clear function is initiated by applying a low
level to either asynchronous clear (ACLR) or
synchronous clear (SCLR). Asynchronous (direct)
clearing overrides all other functions of the device,
while synchronous clearing overrides only the
other synchronous functions. Data is loaded from
the A, B, C, and D inputs by holding load (LOAD)
low during a positive-going clock transition. The
counting function is enabled only when enable P
(ENP) and enable T (ENT) are low and ACLR,
SCLR, and LOAD are high. The up/down (U/D)
input controls the direction of the count. These
counters count up when U/D is high and count
down when U/D is low.
A high level at the output-enable (OE) input forces the Q outputs into the high-impedance state, and a low level
enables those outputs. Counting is independent of OE. ENT is fed forward to enable the ripple-carry output
(RCO) to produce a low-level pulse while the count is zero (all Q outputs low) when counting down or maximum
(9 or 15) when counting up. The clocked carry output (CCO) produces a low-level pulse for a duration equal to
that of the low level of the clock when RCO is low and the counter is enabled (both ENP and ENT are low);
otherwise, CCO is high. CCO does not have the glitches commonly associated with a ripple-carry output.
Cascading is normally accomplished by connecting RCO or CCO of the first counter to ENT of the next counter.
However, for very high-speed counting, RCO should be used for cascading since CCO does not become active
until the clock returns to the low level.
The SN54ALS569A is characterized for operation over the full military temperature range of –55°C to 125°C.
The SN74ALS568A and SN74ALS569A are characterized for operation from 0°C to 70°C.