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Texas Instruments SN74ALS229BN
- Part No.:
- SN74ALS229BN
- Manufacturer:
- Texas Instruments
- Category:
- FIFOs Memory
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS229BN.pdf
- Description:
- IC FIFO ASYNC 16X5 30NS 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,201
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Product details
Overview
SN74ALS229BN from Texas Instruments is a 16 × 5 asynchronous first-in, first-out (FIFO) memory IC with independent write/read clocks, 3-state outputs, and full/empty status flags. It operates at data rates up to 40 MHz, features 14 ns typical fall-through time, and is specified for 0°C to 70°C industrial temperature range. It serves as a buffer in high-speed serial-to-parallel data alignment systems.
For engineers reviewing the SN74ALS229BN datasheet, SN74ALS229BN pinout, SN74ALS229BN application, or SN74ALS229BN equivalent, this device is critical for clock-domain bridging in legacy TTL-based communication interfaces, real-time data buffering, and burst-mode protocol adaptation where deterministic latency and flag-driven flow control are required.
Technical Context
The SN74ALS229BN implements a dual-clock FIFO using advanced low-power Schottky (ALS) logic with a 16-word × 5-bit RAM array and ring-counter-based pointer management. Its asynchronous LDCK and UNCK inputs allow independent write and read timing, while FULL, EMPTY, FULL–2, and EMPTY+2 flags provide precise occupancy monitoring without external logic.
It uses TTL-compatible input thresholds (VIH = 2 V min, VIL = 0.8 V max), delivers 24 mA sink capability on Q outputs, and supports 3-state output enable (OE) with 2 ns enable/disable times. Reset (RST) initializes stack pointers and asserts EMPTY while deasserting FULL and status flags - but leaves Q outputs floating.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Depth × Width | 16 words × 5 bits - provides 80-bit buffer capacity for word-parallel data streams with minimal latency overhead. |
| Max Clock Frequency | 40 MHz for both LDCK and UNCK - enables real-time buffering of high-speed serial links operating up to 200 Mbps aggregate (5 bits × 40 MHz). |
| Fall-Through Time | 14 ns typical - defines minimum delay between valid write and first readable output, critical for pipeline synchronization. |
| Output Drive Strength | 24 mA sink / –1.6 mA source on Q outputs - ensures robust fanout into standard TTL loads without external buffers. |
| Status Flag Logic | Active-low FULL and EMPTY, active-low FULL–2 (14 words) and EMPTY+2 (2 words remaining) - enables hardware flow control with programmable watermark thresholds. |
| Supply Voltage Range | 4.5 V to 5.5 V - compatible with legacy 5 V TTL systems and tolerant of rail droop during transient load conditions. |
| Operating Temperature | 0°C to 70°C - qualified for commercial and industrial equipment environments without derating. |
Pinout & Package
SN74ALS229BN is supplied in a 300-mil plastic dual in-line package (PDIP) with 20 leads, pin-compatible with industry-standard 20-pin DIP sockets and wave-solder assembly processes.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | OE (Output Enable) | Active-low 3-state control for Q0–Q4 outputs; does not affect status flag outputs. |
| 2 | FULL–2 | Active-low flag asserted when exactly 14 words stored - used for early-full warning in flow-controlled systems. |
| 3 | FULL | Active-low flag asserted when memory contains 16 words - halts further writes on LDCK until space becomes available. |
| 4 | LDCK (Load Clock) | Low-to-high edge triggers write of D0–D4 into next available location; ignored when FULL is active. |
| 5–9 | D0–D4 | 5-bit parallel data inputs synchronized to LDCK rising edge; latched on positive transition. |
| 10 | GND | Ground reference for all logic and power domains. |
| 11 | VCC | +5 V supply pin; decoupling capacitor required within 1 cm for stable 40 MHz operation. |
| 12–14 | Q0–Q2 | 3-bit subset of 5-bit parallel data outputs; noninverting, 3-state controlled by OE. |
| 15–16 | Q3–Q4 | Remaining 2 bits of 5-bit parallel output bus; identical electrical behavior to Q0–Q2. |
| 17 | UNCK (Unload Clock) | Low-to-high edge triggers read of oldest word onto Q0–Q4; ignored when EMPTY is active. |
| 18 | EMPTY | Active-low flag asserted when zero words stored - prevents invalid reads and enables empty-state handshaking. |
| 19 | EMPTY+2 | Active-low flag asserted when only two words remain - signals near-empty condition for preemptive refill scheduling. |
| 20 | RST (Reset) | Asynchronous active-low reset that clears internal pointers, forces EMPTY low, and sets FULL/FULL–2/EMPTY+2 high. |
Key Features
| Feature | Design Value |
|---|---|
| Independent Asynchronous Clocks | Separate LDCK and UNCK inputs enable seamless bridging between unrelated clock domains (e.g., UART TX vs. system bus). |
| Four-Level Status Flag Set | FULL, EMPTY, FULL–2, and EMPTY+2 provide granular occupancy feedback for adaptive flow control without software polling. |
| TTL-Compatible ALS Technology | Combines Schottky-clamped speed (40 MHz) with low power consumption (ICC = 85–140 mA) versus standard LS logic. |
| Noninverting 3-State Outputs | Q0–Q4 mirror D0–D4 polarity and enter high-impedance state when OE is low - simplifies bus sharing in multi-device systems. |
| Deterministic Fall-Through Timing | 14 ns typical delay from LDCK↑ to valid Q output ensures predictable latency for real-time interrupt-driven data handling. |
Applications
| UART Data Buffering | Legacy Bus Interface Adapter |
|---|---|
|
Use Scenario: Buffering variable-length packets between a slow microcontroller UART and a high-speed peripheral interface. IC Role / Device Role / Timing Role: Asynchronous FIFO providing clock-domain isolation between MCU's 1.8432 MHz UART clock and 20 MHz system bus clock. Use Value: Eliminates CPU polling or interrupts for every byte; enables burst transfers using FULL/EMPTY flags to manage backpressure. |
Use Scenario: Adapting 8-bit ISA bus timing to 5-bit parallel video data stream from legacy graphics controller. IC Role / Device Role / Timing Role: Word-width converter and rate-matching buffer synchronizing 8-MHz ISA strobes with 40-MHz pixel clock domain. Use Value: Prevents data loss during bus arbitration gaps; FULL–2/EMPTY+2 flags allow pre-emptive DMA reload before underflow/overflow. |
| Industrial Serial Protocol Bridge | Test Equipment Pattern Generator |
|
Use Scenario: Converting Modbus RTU frames (8N1, 9600 bps) to parallel command words for PLC I/O modules. IC Role / Device Role / Timing Role: Synchronizer converting bit-serial RS-485 input into aligned 5-bit command words for parallel register loading. Use Value: Enables deterministic frame reassembly with hardware handshaking - FULL flag halts incoming Modbus RX until host reads buffer. |
Use Scenario: Storing and replaying calibrated test vectors in automated circuit testers with variable stimulus timing. IC Role / Device Role / Timing Role: Deterministic delay line and pattern sequencer feeding 5-bit control words to DUT interface logic. Use Value: 14 ns fall-through time guarantees sub-cycle timing accuracy; RST allows repeatable vector restart without software intervention. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FIFO memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS229N | Faster propagation (tpd = 4 ns typ), higher ICC (180 mA), AS-series TTL - requires tighter power delivery and heatsinking. | Better suited for >40 MHz burst modes but less tolerant of marginal VCC or temperature drift. | Select when absolute minimum latency dominates over power or thermal constraints. |
| 7205L15 | CMOS-based, 32 × 9 organization, 5 V/3.3 V dual-supply capable, lower ICC (<20 mA), but no FULL–2/EMPTY+2 flags. | Lacks fine-grained occupancy flags; requires external logic or firmware to emulate watermark thresholds. | Select when power efficiency and voltage flexibility outweigh need for hardware flow-control granularity. |
Compared with SN74ALS229BN, SN74AS229N trades higher speed for increased power and reduced noise margin, while 7205L15 offers CMOS efficiency and wider voltage support but removes the hardware-level FULL–2/EMPTY+2 signaling essential for deterministic flow control in hard-real-time systems.
Availability
SN74ALS229BN is available at Aetrix Electronics and suitable for UART buffering, industrial protocol bridging, legacy bus interfacing, and test equipment pattern generation requiring stable component supply across long-lifecycle embedded programs.
Supply support for SN74ALS229BN 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 company founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial and automotive qualification.
The SN74ALS229BN belongs to TI's legacy 74ALS logic family, designed specifically for high-speed, low-power asynchronous data buffering in 5 V TTL systems where deterministic latency and hardware flow control are mandatory.
FAQ
What is the maximum clock frequency supported by SN74ALS229BN for both write and read operations?
The SN74ALS229BN supports up to 40 MHz for both LDCK (write clock) and UNCK (read clock) inputs across the full 0°C to 70°C operating range. This specification is verified under CL = 50 pF and VCC = 4.5 V to 5.5 V, with pulse widths meeting minimum 10 ns high/15 ns low requirements. Exceeding 40 MHz may result in metastability or pointer misalignment.
How does the SN74ALS229BN handle simultaneous write and read operations?
The SN74ALS229BN natively supports concurrent write and read via fully independent LDCK and UNCK inputs - no arbitration logic is needed. Its dual-ring-counter architecture ensures atomic pointer updates, preventing race conditions. When FULL is active, LDCK edges are ignored; when EMPTY is active, UNCK edges are ignored - guaranteeing data integrity without external handshaking.
What happens to the Q outputs during reset (RST) of the SN74ALS229BN?
During an active-low RST pulse, the SN74ALS229BN resets internal write and read pointers and forces EMPTY low and FULL, FULL–2, and EMPTY+2 high. However, the Q0–Q4 outputs are **not** driven to any defined logic level - they remain in their last latched state or float depending on OE status. Valid data appears only after the first LDCK↑ following reset or an empty condition.
Can SN74ALS229BN be cascaded to increase word depth beyond 16 words?
No, the SN74ALS229BN does not support cascading in the word-depth direction. The datasheet explicitly states "cascading is easily accomplished in the word-width direction but is not possible in the word-depth direction." To expand depth, external control logic and multiple devices with synchronized clocks and pointer coordination would be required - which is not supported by the SN74ALS229BN's native interface.
What is the meaning of the FULL–2 and EMPTY+2 flags on the SN74ALS229BN?
FULL–2 is an active-low flag that asserts when exactly 14 words are stored - signaling "nearly full" to initiate early flow control. EMPTY+2 is also active-low and asserts when only two words remain - indicating "nearly empty" to trigger preemptive reload. These flags enable hardware-based watermark management without CPU intervention, reducing latency in real-time buffering applications using the SN74ALS229BN.
SN74ALS229BN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Size:
- 80 (16 x 5)
- Function:
- Asynchronous
- Data Rate:
- 40MHz
- Access Time:
- 30ns
- Voltage - Supply:
- 4.5 V ~ 5.5 V
- Current - Supply (Max):
- 140mA
- Bus Directional:
- Uni-Directional
- Expansion Type:
- Width
- Programmable Flags Support:
- No
- Retransmit Capability:
- No
- FWFT Support:
- No
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS229BN FAQ
1.How can I place an order for SN74ALS229BN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS229BN 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 SN74ALS229BN reliable?
The price and inventory of SN74ALS229BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS229BN is usually 5 days.
3.What payment methods are accepted for SN74ALS229BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS229BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS229BN?
SN74ALS229BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS229BN 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 SN74ALS229BN?
For technical support, including SN74ALS229BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS229BN requirements.
6.How does Aetrix verify that SN74ALS229BN is sourced from the original manufacturer or authorized distributors?
All SN74ALS229BN 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 SN74ALS229BN meets industry standards.
7.What is the process for return or replacement of SN74ALS229BN?
All SN74ALS229BN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS229BN, 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 SN74ALS229BN part is unused and in its original packaging.
Return procedure for SN74ALS229BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS229BN Tags
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7201LA15JGI
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7204L12JG
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72V82L15PAG8
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7205L15JGI
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7208L20JG
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72V2105L10PFG
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72V2111L15PFGI
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72V2113L6PFG
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72V36110L6PFG
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SN74ALVC7804-40DL
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7202LA25JGI
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SN74V245-15PAG
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