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Product details

Parameters

Function Counter Bits (#) 8 Technology Family ALS VCC (Min) (V) 4.5 VCC (Max) (V) 5.5 Input type TTL Output type CMOS open-in-new Find other Counter, arithmetic & parity function ICs

Package | Pins | Size

SOIC (DW) 24 160 mm² 15.5 x 10.3 open-in-new Find other Counter, arithmetic & parity function ICs

Features

  • Fully Programmable With Synchronous Counting and Loading
  • SN74ALS867A and ´AS867 Have Asynchronous Clear; SN74ALS869 and ´AS869 Have Synchronous Clear
  • Fully Independent Clock Circuit Simplifies Use
  • Ripple-Carry Output for n-Bit Cascading
  • Package Options Include Plastic Small-Outline (DW) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (NT) and Ceramic (JT) 300-mil DIPs

 

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Description

These synchronous, presettable, 8-bit up/down counters feature internal-carry look-ahead circuitry for cascading in high-speed counting applications. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincidentally with each other when so instructed by the count-enable (,) inputs and internal gating. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters. A buffered clock (CLK) input triggers the eight flip-flops on the rising (positive-going) edge of the clock waveform.

These counters are fully programmable; they may be preset to any number between 0 and 255. The load-input circuitry allows parallel loading of the cascaded counters. Because loading is synchronous, selecting the load mode disables the counter and causes the outputs to agree with the data inputs after the next clock pulse.

The carry look-ahead circuitry provides for cascading counters for n-bit synchronous applications without additional gating. Two count-enable (and ) inputs and a ripple-carry () output are instrumental in accomplishing this function. Both and must be low to count. The direction of the count is determined by the levels of the select (S0, S1) inputs as shown in the function table. is fed forward to enable . thus enabled produces a low-level pulse while the count is zero (all outputs low) counting down or 255 counting up (all outputs high). This low-level overflow-carry pulse can be used to enable successive cascaded stages. Transitions at and are allowed regardless of the level of CLK. All inputs are diode clamped to minimize transmission-line effects, thereby simplifying system design.

These counters feature a fully independent clock circuit. With the exception of the asynchronous clear on the SN74ALS867A and ´AS867, changes at S0 and S1 that modify the operating mode have no effect on the Q outputs until clocking occurs. For the ´AS867 and ´AS869, any time ENP\ and/or ENT\ is taken high, either goes or remains high. For the SN74ALS867A and SN74ALS869, any time is taken high, either goes or remains high. The function of the counter (whether enabled, disabled, loading, or counting) is dictated solely by the conditions meeting the stable setup and hold times.

 

The SN54AS867 and SN54AS869 are characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALS867A, SN74ALS869, SN74AS867, and SN74AS869 are characterized for operation from 0°C to 70°C.

 

 

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Technical documentation

= Top documentation for this product selected by TI
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Type Title Date
* Datasheet Synchronous 8-Bit Up/Down Counters datasheet (Rev. C) Jan. 01, 1995
Selection guide Logic Guide (Rev. AB) Jun. 12, 2017
Application note Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) Dec. 02, 2015
User guide LOGIC Pocket Data Book (Rev. B) Jan. 16, 2007
Application note Semiconductor Packing Material Electrostatic Discharge (ESD) Protection Jul. 08, 2004
More literature Logic Cross-Reference (Rev. A) Oct. 07, 2003
Application note TI IBIS File Creation, Validation, and Distribution Processes Aug. 29, 2002
Application note Bus-Interface Devices With Output-Damping Resistors Or Reduced-Drive Outputs (Rev. A) Aug. 01, 1997
Application note Designing With Logic (Rev. C) Jun. 01, 1997
Application note Input and Output Characteristics of Digital Integrated Circuits Oct. 01, 1996
Application note Live Insertion Oct. 01, 1996
Application note Advanced Schottky (ALS and AS) Logic Families Aug. 01, 1995

Design & development

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Hardware development

EVALUATION BOARD Download
10
Description
This EVM is designed to support any logic device that has a D, DW, DB, NS, PW, P, N, or DGV package in a 14 to 24 pin count.
Features
  • Board design allows for versatility in evaluation
  • Supports a wide-range of logic devices

CAD/CAE symbols

Package Pins Download
SOIC (DW) 24 View options

Ordering & quality

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