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Texas Instruments SN74ALS29854DWR
- Part No.:
- SN74ALS29854DWR
- Manufacturer:
- Texas Instruments
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS29854DWR.pdf
- Description:
- IC TXRX INVERT 5.25V 24SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,970
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Product details
Overview
SN74ALS29854DWR from Texas Instruments is an 8-bit to 9-bit parity bus transceiver with integrated odd-parity generation and checking, open-collector ERR flag output, latch-enable (LE) and clear (CLR) control, and dual-directional A↔B data transfer. It operates at 4.75–5.25 V, supports 0°C to 70°C ambient, and delivers ≤13 ns propagation delay (CL = 300 pF) in SOIC-24 package. It is used in legacy industrial backplanes and fault-tolerant data buses requiring real-time parity error detection and flag storage.
For engineers reviewing the SN74ALS29854DWR datasheet, SN74ALS29854DWR pinout, SN74ALS29854DWR application, or SN74ALS29854DWR equivalent, key selection criteria include open-collector ERR assertion timing (tPHL/tPLH ≤20 ns), inverted-parity diagnostic mode, latch-controlled error flag retention, and compatibility with ALS logic voltage thresholds (VIH = 2 V, VIL = 0.8 V).
Technical Context
The SN74ALS29854DWR implements a synchronous 9-bit parity engine: eight data bits plus one parity bit are processed across bidirectional A and B ports. Parity generation occurs on A→B transfers; parity checking occurs on B→A transfers with PARITY input, producing ERR low on mismatch. The ERR flag is edge-triggered by LE and asynchronously cleared by CLR.
Its control architecture separates bus isolation (OEA/OEB), error sampling (LE), and flag reset (CLR). When OEA and OEB are both low, A→B transfer occurs with inverted parity - a forced-error mode for system diagnostics. ERR output is open-collector, requiring external pull-up, and functions as both real-time indicator and latched status register.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.75 V to 5.25 V - ensures compatibility with standard 5-V ALS TTL systems and stable operation under rail tolerance. |
| Propagation Delay (A→B) | 8 ns (CL = 50 pF) - enables high-speed bus handshaking in real-time control subsystems. |
| ERR Output Response | 20 ns (Bi/PARITY to ERR, CL = 50 pF) - guarantees timely error detection before next bus cycle. |
| Output Drive (IOL) | 48 mA - supports direct driving of multiple TTL inputs or pull-up networks without buffering. |
| Operating Temperature | 0°C to 70°C - validated for commercial-grade embedded systems and industrial controller chassis. |
| Input Thresholds | VIH = 2.0 V, VIL = 0.8 V - matches ALS family logic levels, eliminating level-shifting in homogeneous TTL designs. |
| Package | SOIC-24 (DW) - surface-mount footprint compatible with automated PCB assembly and space-constrained backplane modules. |
Pinout & Package
SN74ALS29854DWR is housed in a 24-pin plastic small-outline integrated circuit (SOIC) package per JEDEC MS-013, with 300-mil body width and 1.27-mm lead pitch. Pin 1 is marked by beveled corner or dot; pins are numbered counterclockwise from top-left (top view).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OEA | A-side output enable | Active-low control enabling A-port drivers; when high, A outputs go high-impedance. |
| OEB | B-side output enable | Active-low control enabling B-port drivers; when high, B outputs go high-impedance. |
| LE | Latch-enable | Positive-edge triggered strobe capturing current ERR state into internal latch for persistent error reporting. |
| CLR | Asynchronous clear | Active-low signal resetting ERR latch regardless of LE state - critical for error recovery sequences. |
| A1–A8 | A-bus data inputs/outputs | 8-bit bidirectional port connected to local CPU or controller bus; direction controlled by OEA/OEB states. |
| B1–B8 | B-bus data inputs/outputs | 8-bit bidirectional port linked to remote peripheral or memory bus; parity-checked during B→A transfer. |
| PARITY | 9th-bit I/O | Generated odd-parity bit on A→B; expected parity input on B→A; drives or samples same net. |
| ERR | Open-collector error flag | Active-low output indicating parity mismatch on B→A transfer; latched or passed based on LE/CLR timing. |
| VCC | Power supply | +5 V supply pin (Pin 13); decoupling capacitor required within 10 mm for noise immunity. |
| GND | Ground reference | Signal and power ground (Pin 12); must be low-inductance connection to minimize switching noise. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 9-bit parity generator/checker | Eliminates need for external XOR trees or discrete parity ICs, reducing board area and interconnect complexity. |
| Open-collector ERR with latch capability | Enables wired-OR error aggregation across multiple transceivers and supports non-volatile error logging via external microcontroller sampling. |
| Inverted-parity diagnostic mode | When OEA=OEB=L, forces ERR assertion regardless of data - allows hardware-level fault injection testing without software intervention. |
| ALS-compatible input/output thresholds | Ensures seamless interoperability with existing 74ALS, 74F, and 74AS logic families without level translation. |
| 300-pF load-tolerant timing | Maintains ≤13 ns A↔B propagation delay even under heavy capacitive loading typical of long backplane traces. |
Applications
| Industrial Backplane Data Integrity | Legacy CPU Bus Extension |
|---|---|
|
Use Scenario: Data transmission between main CPU module and distributed I/O rack over 20-cm parallel bus with >100 pF trace capacitance. IC Role / Device Role / Timing Role: 8-bit data + parity transceiver performing real-time odd-parity generation on outbound writes and checking on inbound reads; ERR flags single-bit corruption. Use Value: Detects physical layer faults (e.g., connector oxidation, crosstalk) before corrupted data reaches firmware, reducing false alarm rate in safety-monitored PLCs. |
Use Scenario: Extending 8086/80286 local bus to off-board memory expansion card using 24-pin ribbon cable. IC Role / Device Role / Timing Role: Bidirectional bus repeater with parity validation; PARITY pin carries generated bit from CPU side and verifies it on return path. Use Value: Enables hot-plug detection via ERR assertion during card insertion/removal, triggering BIOS-level bus reinitialization without system reset. |
| Fault-Tolerant Diagnostic Subsystem | Redundant Controller Synchronization |
|
Use Scenario: Dual-redundant controller pair comparing status registers via shared parity bus; ERR signals divergence. IC Role / Device Role / Timing Role: Parity comparator feeding ERR to interrupt controller; LE captures first error event; CLR resets after diagnostic routine completes. Use Value: Provides deterministic, hardware-asserted fault indication with <20 ns latency - faster than software CRC polling and immune to CPU lockup. |
Use Scenario: Two identical motion controllers exchanging position commands and checksums over isolated differential bus with local parity verification. IC Role / Device Role / Timing Role: Local parity transceiver validating command integrity before execution; inverted-parity mode validates bus driver health during self-test. Use Value: Confirms bidirectional link integrity prior to synchronized axis movement, preventing mechanical collision due to undetected command corruption. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-bit parity transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM29854PC | Functionally identical pinout and logic, but rated for 0°C to 70°C only; no inverted-parity mode documented in AMD datasheet. | Valid for drop-in replacement where diagnostic inverted-parity is unused; lacks TI's ERR latch timing specification. | Select AM29854PC only if sourcing legacy AMD stock; verify CLR/LE timing against actual board layout parasitics. |
| SN74AS29854DWR | Faster propagation (≤6 ns @ CL=50 pF), higher drive (IOL=64 mA), but consumes ~2× more ICC (140 mA vs. 100 mA max). | Suitable for high-speed backplanes (>20 MHz bus clock), but requires enhanced thermal management and tighter VCC regulation. | Choose SN74AS29854DWR when timing margin is critical and power/thermal budget permits; not recommended for battery-backed or thermally constrained modules. |
Compared with AM29854PC and SN74AS29854DWR, the SN74ALS29854DWR offers optimal balance of speed, power, and diagnostic capability for commercial-temperature industrial backplanes - especially where inverted-parity testing and latch-controlled error persistence are required.
Availability
SN74ALS29854DWR is available at Aetrix Electronics and suitable for industrial backplane data integrity, legacy CPU bus extension, fault-tolerant diagnostic subsystems, and redundant controller synchronization requiring stable component supply and long-term obsolescence support.
Supply support for SN74ALS29854DWR 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 for industrial, automotive, and communications markets.
The SN74ALS29854DWR belongs to TI's legacy 74ALS logic family, designed specifically for high-reliability, medium-speed parallel bus systems requiring hardware-level parity protection and deterministic error signaling.
FAQ
What is the function of the PARITY pin on the SN74ALS29854DWR?
The PARITY pin on the SN74ALS29854DWR serves as a bidirectional 9th-bit interface: during A→B data transfer, it outputs odd-parity of A1–A8; during B→A transfer, it accepts the corresponding parity bit from the B bus for checking. Its state directly determines ERR output behavior - mismatch triggers active-low ERR assertion, and the pin must be driven with correct logic level during each direction of operation to ensure valid parity validation in the SN74ALS29854DWR.
How does the inverted-parity mode work in the SN74ALS29854DWR?
The SN74ALS29854DWR enters inverted-parity mode when both OEA and OEB are low - it generates and outputs the complement of true odd parity on the PARITY pin, guaranteeing ERR goes low regardless of A-bus data content. This forced-error condition enables hardware-level bus driver and interconnect diagnostics without software involvement, and is a unique feature confirmed in the SN74ALS29854DWR function table and logic diagram.
Can the ERR output of the SN74ALS29854DWR drive multiple TTL inputs directly?
Yes - the ERR output of the SN74ALS29854DWR is open-collector rated for 48 mA sink current (IOL), sufficient to drive up to six standard TTL inputs (each requiring ~1.6 mA) with a properly sized external pull-up resistor. However, total capacitive load must remain ≤300 pF to maintain specified 20 ns response time; exceeding this degrades ERR assertion timing in the SN74ALS29854DWR.
What is the minimum pulse width required for LE and CLR on the SN74ALS29854DWR?
The SN74ALS29854DWR requires a minimum 10 ns pulse width for both LE and CLR inputs to ensure reliable latching or clearing of the ERR flag register, as specified in the recommended operating conditions table. Pulses shorter than 10 ns may result in metastability or incomplete state transition, causing intermittent error flag behavior that cannot be guaranteed across temperature and voltage extremes for the SN74ALS29854DWR.
Is the SN74ALS29854DWR RoHS compliant?
Yes - the SN74ALS29854DWR is Pb-Free (RoHS compliant) with CU NIPDAU lead finish and meets JEDEC MSL Level-2-250°C-1 Year moisture sensitivity classification, as documented in TI's official packaging information. This RoHS compliance applies specifically to the DW package variant and is verified for the SN74ALS29854DWR orderable device.
SN74ALS29854DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 24mA, 48mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-SOIC
SN74ALS29854DWR FAQ
1.How can I place an order for SN74ALS29854DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS29854DWR 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 SN74ALS29854DWR reliable?
The price and inventory of SN74ALS29854DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS29854DWR is usually 5 days.
3.What payment methods are accepted for SN74ALS29854DWR?
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4.How is shipping managed for SN74ALS29854DWR?
SN74ALS29854DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS29854DWR 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 SN74ALS29854DWR?
For technical support, including SN74ALS29854DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS29854DWR requirements.
6.How does Aetrix verify that SN74ALS29854DWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS29854DWR 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 SN74ALS29854DWR meets industry standards.
7.What is the process for return or replacement of SN74ALS29854DWR?
All SN74ALS29854DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS29854DWR, 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 SN74ALS29854DWR part is unused and in its original packaging.
Return procedure for SN74ALS29854DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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