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Texas Instruments SN74ALS654-1NT

Name: SN74ALS654-1NT
Brand: Texas Instruments
SKU: SN74ALS654-1NT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74ALS654-1NT

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: -

Datasheet:: SN74ALS654-1NT.pdf

Description:: BUS TRANSCEIVER, ALS SERIES

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Product details

Overview

SN74ALS654-1NT from Texas Instruments is an octal bus transceiver and register IC with true-data-path logic, open-collector outputs on the A bus, 3-state outputs on the B bus, and independent clock, select, and output-enable controls for bidirectional multiplexed data management in legacy TTL systems. It operates from 4.5 V to 5.5 V, supports up to 35 MHz clock frequency, and is rated for 0°C to 70°C industrial temperature range in a 24-pin plastic DIP (NT) package.

For engineers reviewing the SN74ALS654-1NT datasheet, SN74ALS654-1NT pinout, SN74ALS654-1NT application, or SN74ALS654-1NT equivalent, this device enables real-time or stored data routing between two 8-bit buses with glitch-free select control, precise timing coordination via CLKAB/CLKBA, and configurable output drive modes - critical for backplane interface, memory-mapped I/O, and synchronous bus arbitration in vintage computing and industrial control designs.

Technical Context

The SN74ALS654-1NT integrates eight identical channels, each combining a D-type flip-flop register, dual-directional transceiver logic, and independent SAB/SBA select control to eliminate decoding glitches during real-time ↔ stored data transitions. Its architecture supports simultaneous storage of A- and B-bus data on low-to-high clock edges, regardless of OE or S state.

It features separate OEAB/OEBA enables for A→B and B→A paths, open-collector A outputs compatible with wired-OR bus structures, and 3-state B outputs for high-impedance isolation. The device uses ALS (Advanced Low-Power Schottky) TTL technology, ensuring compatibility with standard 5-V TTL logic families while delivering improved speed-power tradeoffs over earlier LS variants.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Family	ALS TTL - ensures 5-V TTL interoperability with lower power than LS and higher noise margin than standard TTL.
Bus Width	Octal (8-bit) - supports full parallel data transfer across two independent 8-bit buses (A and B).
A-Bus Output Type	Open-collector - enables wired-OR bus sharing, level translation to lower voltages, and active-low pull-down capability.
B-Bus Output Type	3-state - allows high-impedance tri-state control for shared bus contention avoidance.
Max Clock Frequency	35 MHz - defines maximum synchronous register update rate for stored-data operations.
Propagation Delay	tPLH/tPHL ≤ 64 ns (CLK→A), ≤ 30 ns (CLK→B) - determines worst-case timing budget for synchronous bus handshaking.
Supply Voltage Range	4.5 V to 5.5 V - mandates stable 5-V rail with ±10% tolerance; not compatible with 3.3-V systems without level shifting.
Operating Temperature	0°C to 70°C - qualified for commercial/industrial environments, excluding extended or military-grade operation.

Pinout & Package

SN74ALS654-1NT is housed in a 24-pin plastic dual in-line package (NT), with 300-mil width and through-hole mounting. Pin numbering follows standard DIP orientation (pin 1 at top-left corner, notch or dot marking pin 1 end).

Pin/Terminal	Circuit Role	Design Meaning
1	CLKAB	Clock input controlling storage of A-bus data into internal registers.
2	SAB	Select input determining whether A-bus outputs reflect real-time (low) or stored (high) data.
3	OEAB	Output enable for A-bus drivers; low enables open-collector outputs, high disables (high-Z).
4–11	A1–A8	Open-collector bidirectional I/O pins for A bus; driven low or high-Z, not actively driven high.
12	GND	Ground reference for all logic and power connections.
13	VCC	+5 V supply input; requires local bypass capacitance (0.1 µF ceramic) near pin.
14	CLKBA	Clock input controlling storage of B-bus data into internal registers.
15	SBA	Select input determining whether B-bus outputs reflect real-time (low) or stored (high) data.
16	OEBA	Output enable for B-bus drivers; low enables 3-state outputs, high disables (high-Z).
17–24	B1–B8	3-state bidirectional I/O pins for B bus; actively driven high/low or placed in high-impedance state.

Key Features

Feature	Design Value
Glitch-free select control	Eliminates transient bus contention during SAB/SBA transitions by decoupling select logic from clock domain.
Dual independent clock domains	CLKAB and CLKBA allow asynchronous storage of A- and B-bus data without mutual timing dependency.
Mixed-output topology	Combines open-collector A outputs (for wired-OR, bus arbitration) and 3-state B outputs (for clean high-Z isolation).
Real-time + stored data multiplexing	Four distinct bus-management functions (real-time A↔B, store A/B, transfer stored A/B) enabled via OE/S combinations.
ALS process performance	Delivers 35 MHz max clock rate with typical propagation delays under 30 ns - faster than LS, lower power than AS.
Input-compatible TTL thresholds	VIH = 2.0 V, VIL = 0.8 V - ensures reliable interfacing with legacy 5-V TTL, CMOS, and microcontroller GPIOs.

Applications

Backplane Data Routing	Memory-Mapped I/O Interface
Use Scenario: Isolating and routing 8-bit data between CPU address/data bus and peripheral expansion slots in modular industrial controllers. IC Role / Device Role / Timing Role: Acts as bidirectional bus buffer and register with selectable real-time or latched data path; synchronizes transfers using CLKAB/CLKBA aligned to system clock domain. Use Value: Enables deterministic timing for peripheral read/write cycles while preventing bus contention via independent OEAB/OEBA control and glitch-free SAB/SBA switching.	Use Scenario: Interfacing microprocessor I/O ports to external memory-mapped peripherals requiring synchronized latch control and bus direction management. IC Role / Device Role / Timing Role: Provides registered data capture (via CLKBA) and controlled output enable (OEBA) to meet setup/hold timing of slow peripherals like ADCs or DACs. Use Value: Eliminates need for discrete latches and direction-control logic, reducing component count and PCB area in space-constrained embedded modules.
Legacy System Bus Arbitration	Synchronous Bus Multiplexing
Use Scenario: Managing shared access to a common 8-bit data bus among multiple masters (e.g., CPU, DMA controller, UART) in retro-computing platforms. IC Role / Device Role / Timing Role: Functions as a programmable bus switch with open-collector A outputs enabling wired-OR arbitration signaling and 3-state B outputs for clean master isolation. Use Value: Supports priority-based bus grant protocols using SAB/SBA and OEAB to assert/relinquish bus ownership without external logic.	Use Scenario: Dynamically switching between live sensor data stream and buffered historical values in real-time monitoring systems. IC Role / Device Role / Timing Role: Stores incoming sensor data on CLKAB edges and routes either real-time (SAB = L) or stored (SAB = H) values to display or communication interface via OEAB control. Use Value: Delivers zero-latency real-time view or deterministic snapshot mode without software intervention or CPU overhead.

Backplane Data Routing

Memory-Mapped I/O Interface

Use Scenario: Isolating and routing 8-bit data between CPU address/data bus and peripheral expansion slots in modular industrial controllers.

IC Role / Device Role / Timing Role: Acts as bidirectional bus buffer and register with selectable real-time or latched data path; synchronizes transfers using CLKAB/CLKBA aligned to system clock domain.

Use Value: Enables deterministic timing for peripheral read/write cycles while preventing bus contention via independent OEAB/OEBA control and glitch-free SAB/SBA switching.

Use Scenario: Interfacing microprocessor I/O ports to external memory-mapped peripherals requiring synchronized latch control and bus direction management.

IC Role / Device Role / Timing Role: Provides registered data capture (via CLKBA) and controlled output enable (OEBA) to meet setup/hold timing of slow peripherals like ADCs or DACs.

Use Value: Eliminates need for discrete latches and direction-control logic, reducing component count and PCB area in space-constrained embedded modules.

Legacy System Bus Arbitration

Synchronous Bus Multiplexing

Use Scenario: Managing shared access to a common 8-bit data bus among multiple masters (e.g., CPU, DMA controller, UART) in retro-computing platforms.

IC Role / Device Role / Timing Role: Functions as a programmable bus switch with open-collector A outputs enabling wired-OR arbitration signaling and 3-state B outputs for clean master isolation.

Use Value: Supports priority-based bus grant protocols using SAB/SBA and OEAB to assert/relinquish bus ownership without external logic.

Use Scenario: Dynamically switching between live sensor data stream and buffered historical values in real-time monitoring systems.

IC Role / Device Role / Timing Role: Stores incoming sensor data on CLKAB edges and routes either real-time (SAB = L) or stored (SAB = H) values to display or communication interface via OEAB control.

Use Value: Delivers zero-latency real-time view or deterministic snapshot mode without software intervention or CPU overhead.

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus transceiver and register applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74ALS652A-1NT	True-data-path with 3-state outputs on both A and B buses; no open-collector capability; supports 40 MHz clock.	Lacks wired-OR support; unsuitable where bus arbitration or level translation is required.	Choose when full bidirectional 3-state isolation is needed and open-collector functionality is unnecessary.
SN74ALS653-1NT	Inverting-data-path with open-collector A outputs and 3-state B outputs; same pinout and timing as SN74ALS654-1NT.	Introduces signal inversion on A→B path; incompatible where polarity-sensitive interfaces (e.g., address latching) exist.	Choose only if system-level logic design accommodates inverted A-bus data; otherwise, avoid due to functional mismatch.

Compared with SN74ALS652A-1NT and SN74ALS653-1NT, the SN74ALS654-1NT uniquely provides true-data-path behavior with open-collector A outputs - making it the sole option among these three for applications requiring non-inverted, wired-OR–capable A-bus driving without external pull-ups or inverters.

Availability

SN74ALS654-1NT is available at Aetrix Electronics and suitable for legacy system repair, industrial control retrofitting, and vintage computing restoration requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74ALS654-1NT includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a U.S.-based semiconductor leader founded in 1930, specializing in analog, embedded processing, and logic solutions with deep heritage in TTL and advanced logic families.

The SN74ALS654-1NT belongs to TI's legacy Advanced Low-Power Schottky (ALS) logic product line, designed specifically for high-reliability, medium-speed 5-V TTL bus interface and data routing in industrial, telecom, and computing infrastructure of the 1980s–1990s.

FAQ

What is the primary function of the SN74ALS654-1NT in a digital system?

The SN74ALS654-1NT serves as an octal bus transceiver and register that manages bidirectional data flow between two 8-bit buses (A and B) with selectable real-time or stored data paths. It combines D-type flip-flops for data latching, independent clock inputs (CLKAB/CLKBA), select controls (SAB/SBA), and mixed-output drivers (open-collector A, 3-state B) - enabling flexible bus arbitration, synchronization, and interface consolidation in legacy TTL systems. Its design centers on deterministic timing and glitch-free mode switching.

Does the SN74ALS654-1NT support 3.3-V logic levels?

No, the SN74ALS654-1NT is a 5-V-only ALS TTL device with absolute maximum input voltage of 7 V on control pins and 5.5 V on I/O ports. Its input thresholds (VIH = 2.0 V, VIL = 0.8 V) and output drive characteristics are specified only for 4.5 V to 5.5 V VCC operation. Direct connection to 3.3-V logic requires level-shifting circuitry; it is not 3.3-V tolerant or compatible without external interface components.

How does the SN74ALS654-1NT differ from the SN74ALS653-1NT?

The SN74ALS654-1NT implements a true-data-path logic function, whereas the SN74ALS653-1NT is inverting. Both share identical pinout, open-collector A outputs, 3-state B outputs, and timing specifications. However, SN74ALS653-1NT inverts data transferred from A to B, making it incompatible in systems where signal polarity must be preserved - such as address bus latching or non-inverting control signal distribution. SN74ALS654-1NT is the correct choice for true-path requirements.

Can the SN74ALS654-1NT operate without external pull-up resistors on the A-bus outputs?

No - because the A-bus outputs are open-collector, they require external pull-up resistors to establish valid HIGH logic levels. The value depends on bus capacitance and desired rise time; typical values range from 1.0 kΩ to 4.7 kΩ to +5 V. Without pull-ups, A-bus outputs can only drive LOW or float, resulting in undefined logic states and potential system malfunction.

Is there a surface-mount equivalent to the SN74ALS654-1NT in SOIC or TSSOP packages?

No - the SN74ALS654-1NT is exclusively offered in the 24-pin plastic DIP (NT) package per TI's SDAS066F datasheet. While other members of the family (e.g., SN74ALS654DW) exist in SOIC (DW) format, the "-1NT" suffix explicitly denotes the through-hole NT package. No official TSSOP or smaller footprint variant was released for this specific part number; migration to surface-mount requires redesign using pin-compatible alternatives like SN74ALS654DW, subject to layout and thermal validation.

SN74ALS654-1NT Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: *

Package/Case:: -

Packaging:: Bulk

Product Status:: Active

Logic Type:: -

Number of Elements:: -

Number of Bits per Element:: -

Input Type:: -

Output Type:: -

Current - Output High, Low:: -

Voltage - Supply:: -

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: -

Supplier Device Package:: -

SN74ALS654-1NT FAQ

1.How can I place an order for SN74ALS654-1NT through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74ALS654-1NT on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SN74ALS654-1NT reliable?

The price and inventory of SN74ALS654-1NT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS654-1NT is usually 5 days.

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SN74ALS654-1NT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74ALS654-1NT order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SN74ALS654-1NT?

For technical support, including SN74ALS654-1NT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS654-1NT requirements.

6.How does Aetrix verify that SN74ALS654-1NT is sourced from the original manufacturer or authorized distributors?

All SN74ALS654-1NT products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74ALS654-1NT meets industry standards.

7.What is the process for return or replacement of SN74ALS654-1NT?

All SN74ALS654-1NT units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS654-1NT, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SN74ALS654-1NT part is unused and in its original packaging.

Return procedure for SN74ALS654-1NT:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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