SN54ALS561A, SN74ALS561A SYNCHRONOUS 4-BIT COUNTERS WITH 3-STATE OUTPUTS

SDAS225A - DECEMBER 1982 - REVISED JANUARY 1995

features

Carry Output for n-Bit Cascading
Buffer-Type Outputs Drive Bus Lines Directly
Choice of Asynchronous or Synchronous Clearing and Loading
Internal Look-Ahead Circuitry for Fast Cascading
Package Options Include Plastic Small-Outline (DW) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (N) and Ceramic (J) 300-mil DIPs

description

These binary counters are programmable and offer synchronous andasynchronous clearing as well as synchronous and asynchronousloading. All synchronous functions are executed on the positive-goingedge of the clock.

The clear function is initiated by applying a low level to eitherasynchronous clear (ACLR\) or synchronous clear (SCLR\). ACLR\(direct clear) overrides all other functions of the device, whileSCLR\ overrides only the other synchronous functions. Data is loadedfrom the A, B, C, and D inputs by applying a low level toasynchronous load (ALOAD\) or by the combination of a low level atsynchronous load (SLOAD\) and a positive-going clock transition. Thecounting function is enabled only when enable P (ENP), enable T(ENT), ACLR\, ALOAD\, SCLR\, and SLOAD\ are all high.

A high level at the output-enable () input forces the Q outputs intothe high-impedance state, and a low level enables those outputs.Counting is independent of OE\. ENT is fed forward to enable theripple-carry output (RCO) to produce a high-level pulse while thecount is maximum (15). The clocked carry output (CCO) produces ahigh-level pulse for a duration equal to that of the low level of theclock when RCO is high and the counter is enabled (ENP and ENT arehigh); otherwise, CCO is low. CCO does not have the glitches commonlyassociated with a ripple-carry output. Cascading is normallyaccomplished by connecting RCO or CCO of the first counter to ENT ofthe next counter. However, for very high-speed counting, RCO shouldbe used for cascading because CCO does not become active until theclock returns to the low level.

The SN54ALS561A is characterized for operation over the fullmilitary temperature range of -55°C to 125°C. TheSN74ALS561A is characterized for operation from 0°C to70°C.

Title: SYNCHRONOUS 4-BIT COUNTERS WITH 3-STATE OUTPUTS
Product Family: BINARY
Device Functionality: COUNTER
Orderable Devices: SNJ54ALS561AJ, SN74ALS561ADW, SN74ALS561ADWR, SN74ALS561AN

View the complete PDF datasheet: sdas225a.pdf (146 K Bytes) (Requires Acrobat Reader 3.x)

View more information about generic part numbers:SN54ALS561A, SN74ALS561A

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