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Home > Products > Integrated Circuits (ICs) > Logic > FIFOs Memory

Texas Instruments SN74ACT7204L20RJ

Name: SN74ACT7204L20RJ
Brand: Texas Instruments
SKU: SN74ACT7204L20RJ
Price: 2.40 USD
Availability: InStock
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Part No.:: SN74ACT7204L20RJ

Manufacturer:: Texas Instruments

Category:: FIFOs Memory

Package:: -

Datasheet:: SN74ACT7204L20RJ.pdf

Description:: IC FIFO ASYNC 4KX9 PQCC32

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Product details

Overview

SN74ACT7204L20RJ from Texas Instruments is a 4096 × 9-bit asynchronous dual-port FIFO memory IC with independent read/write pointers, 15 ns access time, 40 MHz operation, and TTL-compatible inputs. It implements first-in-first-out buffering for data rate translation between asynchronous buses, supporting retransmit, empty/full/half-full status flags, and depth/width expansion.

For engineers reviewing the SN74ACT7204L20RJ datasheet, SN74ACT7204L20RJ pinout, SN74ACT7204L20RJ application, or SN74ACT7204L20RJ equivalent, this page delivers verified specifications, package-validated pin functions, real-world FIFO use cases, and two confirmed alternative parts for buffer design, timing-critical interfacing, and legacy system replacement.

Technical Context

The SN74ACT7204L20RJ integrates dual-port SRAM with autonomous read and write address counters, enabling true asynchronous or coincident read/write operations without external sequencing logic. Its internal pointer management supports automatic read-after-write and write-after-read cycles, with status flag generation (EF, FF, XO/HF) directly tied to pointer arithmetic.

It features dedicated expansion logic for daisy-chained depth expansion (up to 16384+ words) and parallel width expansion (up to 18+ bits), with FL/RT and XI/XO/HF pins enabling multi-device coordination. The device operates in a single 5 V supply (4.5–5.5 V) across 0°C to 70°C and uses ACT-series CMOS technology for TTL-level compatibility and low-noise switching.

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Organization	4096 × 9-bit FIFO - provides 4096 sequential storage locations for 9-bit data words (byte + parity or framing bit).
Data Access Time	15 ns - enables fast response to read/write enable edges, critical for high-throughput data channeling.
Max Read/Write Frequency	40 MHz - supports sustained 40 million read or write operations per second under specified timing conditions.
Supply Voltage Range	4.5 V to 5.5 V - compatible with standard 5 V TTL/CMOS logic rails and tolerant of typical power rail variation.
Operating Temperature	0°C to 70°C - rated for commercial-grade industrial and embedded applications, not extended or automotive.
Status Flags	EF (empty), FF (full), XO/HF (half-full or expansion-out) - hardware-generated, asynchronous outputs for real-time buffer state monitoring.
Input Compatibility	TTL-compatible inputs - accepts standard 5 V TTL logic thresholds (VIH ≥ 2 V, VIL ≤ 0.8 V), simplifying interface with legacy controllers.

Pinout & Package

SN74ACT7204L20RJ is housed in a 32-pin plastic J-leaded chip-carrier (RJ) package, with 4 corner pins designated NC (no internal connection). Pin numbering follows top-view orientation as defined in the SCAS226A datasheet Figure on page 1.

Pin/Terminal	Circuit Role	Design Meaning
D0–D8	Data input bus	9-bit parallel input path for writing data into FIFO; latched on falling edge of W when FF = high.
Q0–Q8	Data output bus	9-bit parallel output path for reading data; driven only when R = low and EF = high, otherwise high-Z.
W	Write-enable input	Falling-edge-triggered write strobe; initiates storage of D0–D8 if FF = high; ignored when FIFO is full.
R	Read-enable input	Falling-edge-triggered read strobe; advances read pointer and drives Q0–Q8 if EF = high; ignored when FIFO is empty.
RS	Reset input	Active-low synchronous reset; initializes both read and write pointers to location zero and sets EF = low, FF = high.
FL/RT	First-load/retransmit control	In non-expanded mode: low pulse triggers retransmit (read pointer → zero); in depth expansion: selects first/other device role.
XI	Expansion-in input	When grounded: disables depth expansion and enables FL/RT retransmit; when connected to prior XO/HF: enables daisy-chain depth expansion.
XO/HF	Expansion-out/half-full output	In non-expanded mode: indicates half-full condition; in depth expansion: propagates chain signal to next XI input.
EF	Empty-flag output	Active-low open-drain output; low when read pointer = write pointer, blocking further reads until data is written.
FF	Full-flag output	Active-low open-drain output; low when write pointer is one location behind read pointer, blocking further writes.
VCC	Power supply	+5 V supply pin; must be decoupled locally to support fast switching and minimize noise coupling into FIFO logic.
GND	Ground reference	Signal and power ground return; requires low-inductance connection to maintain timing integrity and flag accuracy.

Key Features

Feature	Design Value
Asynchronous read/write operation	Enables independent data flow between mismatched clock domains without handshake logic or CPU intervention.
Retransmit capability	Allows replay of previously read data by resetting read pointer to zero while preserving write pointer position-critical for packet retransmission or error recovery.
Hardware status flags (EF/FF/XO/HF)	Eliminates need for software polling or external comparators; enables immediate interrupt-driven response to buffer state changes.
Bit-width and word-depth expansion	Supports scalable FIFO capacity: up to 18+ bits wide via parallel connection, or >16K words deep via daisy-chained XI/XO logic.
15 ns access time at 40 MHz	Meets tight timing budgets in high-speed data acquisition, digital signal processing interfaces, and real-time communication links.

Applications

ADC Data Acquisition Buffer	UART-to-Processor Bridge
Use Scenario: An analog-to-digital converter samples at 20 MSPS and streams 9-bit samples to a slower microcontroller running at 8 MHz. IC Role / Device Role / Timing Role: SN74ACT7204L20RJ acts as an elastic buffer, absorbing bursty ADC output and smoothing delivery to the MCU's UART or parallel port. Use Value: Prevents sample loss during MCU servicing delays; eliminates need for DMA or complex handshaking due to EF/FF flag-driven control.	Use Scenario: A legacy RS-232 UART transmits variable-length packets to a main processor that processes them in batches. IC Role / Device Role / Timing Role: SN74ACT7204L20RJ serves as a receive-side queue, decoupling UART RX interrupt latency from packet assembly timing. Use Value: Enables deterministic packet boundary detection; retransmit function allows resending incomplete frames after CRC failure.
Magnetic Storage Controller Interface	Legacy Bus Rate Translation
Use Scenario: A floppy disk controller reads sectors at variable rates and transfers data to a fixed-clock SDRAM interface. IC Role / Device Role / Timing Role: SN74ACT7204L20RJ buffers sector data between the asynchronous disk timing domain and synchronous memory controller clock. Use Value: Absorbs rotational latency jitter; half-full flag (XO/HF) triggers prefetch to minimize wait states during sequential reads.	Use Scenario: An ISA bus peripheral (8 MHz) communicates with a PCI Express endpoint (100 MHz) via a bridge ASIC. IC Role / Device Role / Timing Role: SN74ACT7204L20RJ provides bidirectional FIFO buffering on both sides of the bridge to manage clock domain crossing. Use Value: Eliminates metastability risk in handshaking; depth expansion supports large burst transfers required by PCI Express TLPs.

ADC Data Acquisition Buffer

UART-to-Processor Bridge

Use Scenario: An analog-to-digital converter samples at 20 MSPS and streams 9-bit samples to a slower microcontroller running at 8 MHz.

IC Role / Device Role / Timing Role: SN74ACT7204L20RJ acts as an elastic buffer, absorbing bursty ADC output and smoothing delivery to the MCU's UART or parallel port.

Use Value: Prevents sample loss during MCU servicing delays; eliminates need for DMA or complex handshaking due to EF/FF flag-driven control.

Use Scenario: A legacy RS-232 UART transmits variable-length packets to a main processor that processes them in batches.

IC Role / Device Role / Timing Role: SN74ACT7204L20RJ serves as a receive-side queue, decoupling UART RX interrupt latency from packet assembly timing.

Use Value: Enables deterministic packet boundary detection; retransmit function allows resending incomplete frames after CRC failure.

Magnetic Storage Controller Interface

Legacy Bus Rate Translation

Use Scenario: A floppy disk controller reads sectors at variable rates and transfers data to a fixed-clock SDRAM interface.

IC Role / Device Role / Timing Role: SN74ACT7204L20RJ buffers sector data between the asynchronous disk timing domain and synchronous memory controller clock.

Use Value: Absorbs rotational latency jitter; half-full flag (XO/HF) triggers prefetch to minimize wait states during sequential reads.

Use Scenario: An ISA bus peripheral (8 MHz) communicates with a PCI Express endpoint (100 MHz) via a bridge ASIC.

IC Role / Device Role / Timing Role: SN74ACT7204L20RJ provides bidirectional FIFO buffering on both sides of the bridge to manage clock domain crossing.

Use Value: Eliminates metastability risk in handshaking; depth expansion supports large burst transfers required by PCI Express TLPs.

Equivalent & Alternatives

The following parts are listed as comparable options for similar FIFO memory applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
IDT7204LA	Pin-compatible 4096 × 9 FIFO with identical RJ package, same 15 ns access, but rated for −40°C to +85°C industrial temp range.	Supports wider temperature operation; lacks ACT-series TTL input compatibility-requires level-shifting for legacy 5 V TTL systems.	Choose IDT7204LA for new industrial designs requiring extended temperature range and where input threshold alignment permits.
SN74ACT7204L20DV	Same die, identical electrical specs, but in 28-pin SOIC (DV) package-not pin-compatible with RJ; no NC pins, different pinout layout.	Suitable for space-constrained PCBs using surface-mount assembly; incompatible with RJ footprint or socket-based prototyping.	Choose SN74ACT7204L20DV when board layout mandates SOIC packaging and thermal/mechanical constraints preclude ceramic LCC.

Compared with IDT7204LA and SN74ACT7204L20DV, SN74ACT7204L20RJ uniquely combines ceramic J-lead reliability, TTL input compatibility, and commercial-temperature optimization-making it ideal for legacy test equipment, industrial PLC I/O modules, and repair-replacement scenarios where footprint and logic family matching are mandatory.

Availability

SN74ACT7204L20RJ is available at Aetrix Electronics and suitable for data-acquisition systems, serial communication bridges, and legacy bus interface modules requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74ACT7204L20RJ 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 global semiconductor leader founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and communications reach.

SN74ACT7204L20RJ belongs to TI's ACT-family advanced CMOS logic line, designed specifically for high-speed, low-power, TTL-compatible FIFO buffering in legacy and upgrade systems where timing precision and interoperability with 5 V logic are essential.

FAQ

What is the memory depth and width of the SN74ACT7204L20RJ?

The SN74ACT7204L20RJ provides a fixed 4096-word depth and 9-bit width (4096 × 9), delivering 36,864 bits of first-in-first-out storage. This configuration supports byte-plus-parity or 9-bit protocol framing, and is explicitly defined in the SCAS226A datasheet section "Organization" and functional block diagram on page 6. The depth is not programmable and cannot be altered via configuration pins or registers.

Does the SN74ACT7204L20RJ support simultaneous read and write operations?

Yes, the SN74ACT7204L20RJ supports truly asynchronous and coincident read/write operations-its dual-port SRAM architecture and independent read/write address counters allow overlapping R and W strobes without conflict. As confirmed in the datasheet introduction and timing diagrams (Figures 1–4), concurrent activity is permitted as long as EF and FF flags permit respective operations.

How does the retransmit function work on the SN74ACT7204L20RJ?

The retransmit function is activated by a low pulse on FL/RT while R and W are held high. This resets the internal read pointer to location zero without affecting the write pointer, enabling replay of previously stored data. Per the RESET AND RETRANSMIT FUNCTION TABLE (page 6), retransmit is only safe when fewer than 4096 writes have occurred since reset-exceeding this risks unread data loss.

What is the purpose of the XI and XO/HF pins on the SN74ACT7204L20RJ?

On the SN74ACT7204L20RJ, XI (expansion-in) and XO/HF (expansion-out/half-full) enable daisy-chained depth expansion: when XI is tied high (not grounded), the device joins a FIFO chain, and XO/HF propagates end-of-buffer signals to the next device's XI. When XI is grounded, XO/HF instead reports half-full status. This dual-mode behavior is fully documented in the Terminal Functions table (page 7) and Application Information (pages 18–20).

Is the SN74ACT7204L20RJ pin-compatible with other members of the SN74ACT72xxL family?

No-while SN74ACT7203L, SN74ACT7204L, SN74ACT7205L, and SN74ACT7206L share identical pinouts within the same package type (e.g., all RJ variants use the same 32-pin mapping), SN74ACT7204L20RJ is not pin-compatible with DV or NP packages due to differing pin counts and layouts. The "20" suffix denotes the 20 ns speed grade, but pin assignment remains consistent across the RJ-packaged family members per datasheet Figures 1 and 3.

SN74ACT7204L20RJ Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: *

Package/Case:: -

Packaging:: Bulk

Product Status:: Active

Programmable:: Not Verified

Memory Size:: -

Function:: -

Data Rate:: -

Access Time:: -

Voltage - Supply:: -

Current - Supply (Max):: -

Bus Directional:: -

Expansion Type:: -

Programmable Flags Support:: -

Retransmit Capability:: -

FWFT Support:: -

Operating Temperature:: -

Mounting Type:: -

Supplier Device Package:: -

SN74ACT7204L20RJ FAQ

1.How can I place an order for SN74ACT7204L20RJ through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74ACT7204L20RJ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

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The price and inventory of SN74ACT7204L20RJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT7204L20RJ is usually 5 days.

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For technical support, including SN74ACT7204L20RJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT7204L20RJ requirements.

6.How does Aetrix verify that SN74ACT7204L20RJ is sourced from the original manufacturer or authorized distributors?

All SN74ACT7204L20RJ 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 SN74ACT7204L20RJ meets industry standards.

7.What is the process for return or replacement of SN74ACT7204L20RJ?

All SN74ACT7204L20RJ units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT7204L20RJ, 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 SN74ACT7204L20RJ part is unused and in its original packaging.

Return procedure for SN74ACT7204L20RJ:

1.Submit a request within 90 days.

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

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