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NXP Semiconductors SCC2691AC1A28,518
- Part No.:
- SCC2691AC1A28,518
- Manufacturer:
- NXP Semiconductors
- Package:
- 28-LCC (J-Lead)
- Datasheet:
-
SCC2691AC1A28,518.pdf
- Description:
- IC UART CMOS LSI 28PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,392
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Product details
Overview
SCC2691AC1A28 from NXP Semiconductors (formerly Philips Semiconductors) is a CMOS-LSI universal asynchronous receiver/transmitter (UART) providing full-duplex serial communication with quadruple-buffered receiver, independent receiver/transmitter baud rate selection, and integrated 16-bit counter/timer. It operates from a single +5 V supply, supports 5–8 data bits, 1/1.5/2 stop bits, and odd/even/no parity, and targets legacy industrial control and terminal interface applications.
For engineers reviewing the SCC2691AC1A28 datasheet, SCC2691AC1A28 pinout, SCC2691AC1A28 application, or SCC2691AC1A28 equivalent, key selection considerations include its 28-pin PLCC package, TTL-compatible parallel bus interface (D0–D7, A0–A2, WRN, RDN, CEN), dual-clock domain support (X1/CLK, X2), and programmable channel modes including local/remote loopback and automatic echo.
Technical Context
The SCC2691AC1A28 implements a fully synchronous UART architecture with separate clock selectors for receiver and transmitter, enabling true dual-speed operation - e.g., 9600 baud receive / 19200 baud transmit - critical for clustered terminal systems. Its internal crystal oscillator (3.6864 MHz nominal) feeds both the baud rate generator (18 fixed rates up to 115.2 kbaud) and a 16-bit counter/timer configurable as timer or event counter.
Receiver functionality includes quadruple buffering (3-character FIFO + shift register), false start bit detection, line break generation/detection, and RTSN flow control auto-negation on FIFO full condition. Transmitter supports break generation, programmable A/D bit for multi-processor address framing, and TxRDY signaling via MPO pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Baud Rates | 18 fixed rates (50–115.2 kbaud); also supports non-standard rates via 16-bit counter/timer or external 1X/16X clock - enables precise timing for legacy protocols. |
| Data Format | 5–8 data bits, 1/1.5/2 stop bits (1/16-bit programmable), odd/even/no/force parity - ensures compatibility with RS-232, RS-422, and proprietary serial interfaces. |
| Receiver Buffering | Quadruple-buffered (3-deep FIFO + shift register) - reduces interrupt overhead and prevents overrun in interrupt-driven systems at up to 115.2 kbaud. |
| Power Supply | +5 V ±10%; active current ≤2.5 mA (industrial), power-down current ≤500 µA - suitable for low-power embedded systems with sleep/wake cycles. |
| Operating Temperature | –40°C to +85°C (industrial grade) - validated for deployment in factory automation, motor drives, and outdoor telemetry equipment. |
| Package | 28-pin Plastic Leaded Chip Carrier (PLCC), 11.5 mm × 11.5 mm, J-lead - surface-mount compatible with reflow assembly and high-reliability board layouts. |
| Interrupt Logic | Single open-drain INTRN output with 7 maskable sources (TxRDY, RxRDY/FFULL, break, MPI change, counter TC, etc.) - simplifies CPU interrupt handling with status register (ISR) decoding. |
Pinout & Package
SCC2691AC1A28 is housed in a 28-pin PLCC (SOT261-2) package with J-leads, designed for surface-mount assembly and thermal reliability in industrial environments. Pin 1 is located at the index corner adjacent to the notch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | VCC | +5 V power supply input - must be decoupled locally with 0.1 µF ceramic capacitor to GND. |
| 2, 3 | RxD, TxD | Receiver input / transmitter output - TTL-level serial I/O; RxD accepts inverted RS-232 via external level shifter. |
| 4, 5 | MPO, MPI | Multi-purpose output/input - MPO can source RTSN, Tx/Rx clocks, or counter/timer output; MPI accepts CTSN, RTCLK, or CTCLK. |
| 6–8 | A0–A2 | Register address inputs - select among 8 internal registers (MR1/MR2, SR/CSR, RHR/THR, ISR/IMR, CTU/CTUR, CTL/CTLR, ACR, CR). |
| 9, 10 | X1/CLK, X2 | Clock inputs - accept 3.6864 MHz crystal or external clock; X1/CLK serves as primary timing reference for BRG and counter/timer. |
| 11 | RESET | Active-high master reset - clears status/interrupt registers, disables Tx/Rx, sets mode pointer to MR1, and forces TxD high. |
| 12 | GND | Ground reference - requires low-impedance connection to system ground plane. |
| 13 | INTRN | Open-drain interrupt request - requires external 2.7 kΩ pull-up to VCC; asserts on any enabled interrupt condition. |
| 14 | RESET | Same function as Pin 11 - duplicate RESET pin per PLCC layout (dual-sided access). |
| 15–22 | D0–D7 | 8-bit bidirectional data bus - transfers register contents; direction controlled by WRN (write) and RDN (read) with CEN asserted. |
| 23 | CEN | Chip enable - active-low; isolates D0–D7 in 3-state when high, enabling shared bus operation. |
| 24 | WRN | Write strobe - active-low; latches D0–D7 into selected register on rising edge. |
| 25–28 | RDN, NC, NC, NC | Read strobe (Pin 25); Pins 26–28 are no-connect - reserved for internal test or future variants. |
Key Features
| Feature | Design Value |
|---|---|
| Independent Rx/Tx Baud Rate Control | Enables asymmetric communication (e.g., slow host ↔ fast peripheral) without external clock dividers or dual UARTs. |
| Quadruple-Buffered Receiver | 3-character FIFO + shift register minimizes CPU polling frequency and eliminates overrun at 115.2 kbaud with <10 µs interrupt latency. |
| Programmable Multi-Function I/O (MPO/MPI) | MPO outputs RTSN, Tx/Rx clocks, or counter/timer signal; MPI accepts CTSN or external clock - reduces external logic count by ≥3 components. |
| Integrated Crystal Oscillator | Eliminates need for external oscillator IC; supports direct 3.6864 MHz crystal connection with minimal external load caps (12–22 pF typical). |
| Power-Down Mode | Oscillator freeze preserves register state while reducing ICC from 2.5 mA to ≤500 µA - extends battery life in portable diagnostics tools. |
| Multi-Processor Address Recognition | Configurable A/D bit and address frame detection allow wake-up of slave nodes without continuous polling - cuts system standby current by >90%. |
Applications
| Industrial Serial Gateway | Legacy Terminal Interface |
|---|---|
|
Use Scenario: Connecting PLCs, HMIs, and CNC controllers via RS-232/422 to a central fieldbus gateway. IC Role / Device Role / Timing Role: UART bridging protocol translation; provides hardware flow control (RTSN/CTSN), dual-speed operation for mixed-baud networks, and robust noise immunity via TTL-level signaling with external transceivers. Use Value: Eliminates need for external FIFOs or clock generators; quadruple buffering sustains 115.2 kbaud burst traffic without packet loss in factory-floor EMI environments. |
Use Scenario: Retrofitting aging point-of-sale terminals, barcode scanners, or lab instruments with modern microcontroller hosts. IC Role / Device Role / Timing Role: Legacy serial interface adapter; handles non-standard stop-bit increments (1/16-bit), force parity, and false start bit rejection required by proprietary peripherals. Use Value: Maintains compatibility with 1980s–1990s equipment using 7E1, 8O2, or 5N1 formats - avoids costly firmware rewrites or custom ASIC development. |
| Multi-Node Telemetry Hub | Embedded Diagnostic Port |
|
Use Scenario: Central telemetry unit collecting sensor data from 8+ remote nodes over half-duplex RS-485 links. IC Role / Device Role / Timing Role: Multi-processor UART managing address-based wake-up; uses A/D bit framing to selectively activate slaves and minimize bus contention. Use Value: Reduces average node current from 5 mA to <100 µA during idle; enables battery-powered remote sensors with 5+ year lifespan. |
Use Scenario: In-circuit debug port on medical infusion pumps, motor drives, or avionics LRUs requiring secure firmware updates and real-time logging. IC Role / Device Role / Timing Role: Secure diagnostic interface with local loopback mode for self-test, break detection for emergency halt, and power-down for tamper-resistant sleep states. Use Value: Supports ISO 13485-compliant traceability via timestamped UART logs; local loopback validates physical layer pre-deployment without host PC. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar UART applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SCC2692AC1A28 | Pin-compatible 28-pin PLCC variant with enhanced FIFO (16-byte depth vs. 3-byte), additional interrupt sources, and extended baud rate range up to 230.4 kbaud. | Required for high-throughput industrial gateways needing >100 kbaud sustained throughput and reduced CPU interrupt load. | Select SCC2692AC1A28 only if buffer depth and speed exceed SCC2691AC1A28 capabilities; not drop-in due to register map differences in FIFO control. |
| TL16C550CPTR | TI 16550-compatible UART in 48-pin TQFP; features 16-byte FIFO, auto RTS/CTS, and 1.5 Mbps max rate but lacks integrated oscillator and multi-processor mode. | Suitable for PC-style embedded systems using standard 16550 drivers; incompatible with crystal-less or address-framing designs. | Choose TL16C550CPTR for Linux/Windows driver reuse and high-speed PCMCIA applications; avoid where crystal integration or A/D framing is mandatory. |
Compared with SCC2691AC1A28, SCC2692AC1A28 offers deeper buffering and higher speed but requires firmware adaptation, while TL16C550CPTR delivers industry-standard compatibility at the cost of missing oscillator and multi-processor features - making SCC2691AC1A28 optimal for cost-sensitive, crystal-based, legacy-industrial UART implementations.
Availability
SCC2691AC1A28 is available at Aetrix Electronics and suitable for industrial serial gateways, legacy terminal interfaces, multi-node telemetry hubs, and embedded diagnostic ports requiring stable component supply across extended product lifecycles.
Supply support for SCC2691AC1A28 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
NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications, with roots in Philips' pioneering analog and mixed-signal IC development.
The SCC2691AC1A28 belongs to NXP's legacy communications interface portfolio, designed specifically for robust, low-power, crystal-integrated UART functions in long-lifecycle industrial control and instrumentation systems.
FAQ
What is the maximum supported baud rate for SCC2691AC1A28?
The SCC2691AC1A28 supports up to 115.2 kbaud using its internal baud rate generator or external 16X clock. Non-standard rates up to this limit are achievable via the 16-bit counter/timer; operation beyond 115.2 kbaud is not specified or guaranteed in the official datasheet for SCC2691AC1A28.
Does SCC2691AC1A28 include an integrated crystal oscillator?
Yes, SCC2691AC1A28 integrates a crystal oscillator circuit. It operates directly from a 3.6864 MHz crystal connected between X1/CLK and X2 pins, eliminating the need for an external oscillator IC - a key differentiator from UARTs like the TL16C550CPTR which require external clock sources.
Can SCC2691AC1A28 operate in a multi-processor network?
Yes, SCC2691AC1A28 supports multi-processor communication via address frame recognition mode. When configured with MR1[4:3] = '11', it detects address characters and asserts RxRDY to wake the CPU - enabling selective slave activation without continuous polling, a feature absent in basic 16550-family UARTs.
What is the receiver buffer depth of SCC2691AC1A28?
The SCC2691AC1A28 features a quadruple-buffered receiver consisting of a 3-character FIFO plus the receive shift register. This configuration prevents overrun at 115.2 kbaud under interrupt-driven operation and reduces CPU servicing frequency compared to single-buffer UARTs.
Is SCC2691AC1A28 pin-compatible with other UARTs in the SCC26xx family?
SCC2691AC1A28 shares the same 28-pin PLCC footprint and core register map with SCC2692AC1A28, but differs in FIFO depth, interrupt sources, and counter/timer behavior. While physically mountable, register-level compatibility is partial - firmware validation is required before substitution with SCC2692AC1A28.
SCC2691AC1A28,518 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Package/Case:
- 28-LCC (J-Lead)
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Features:
- Configurable GPIO, Internal Oscillator, Timer/Counter
- Number of Channels:
- 1, UART
- FIFO's:
- -
- Protocol:
- -
- Data Rate (Max):
- -
- Voltage - Supply:
- 5V
- With Auto Flow Control:
- Yes
- With IrDA Encoder/Decoder:
- -
- With False Start Bit Detection:
- Yes
- With Modem Control:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-PLCC (11.48x11.48)
SCC2691AC1A28,518 FAQ
1.How can I place an order for SCC2691AC1A28,518 through Aetrix?
Please submit a Request for Quotation (RFQ) for SCC2691AC1A28,518 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 SCC2691AC1A28,518 reliable?
The price and inventory of SCC2691AC1A28,518 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SCC2691AC1A28,518 is usually 5 days.
3.What payment methods are accepted for SCC2691AC1A28,518?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SCC2691AC1A28,518 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SCC2691AC1A28,518?
SCC2691AC1A28,518 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SCC2691AC1A28,518 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 SCC2691AC1A28,518?
For technical support, including SCC2691AC1A28,518 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SCC2691AC1A28,518 requirements.
6.How does Aetrix verify that SCC2691AC1A28,518 is sourced from the original manufacturer or authorized distributors?
All SCC2691AC1A28,518 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 SCC2691AC1A28,518 meets industry standards.
7.What is the process for return or replacement of SCC2691AC1A28,518?
All SCC2691AC1A28,518 units undergo pre-shipment inspection (PSI). If there is an issue with SCC2691AC1A28,518, 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 SCC2691AC1A28,518 part is unused and in its original packaging.
Return procedure for SCC2691AC1A28,518:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SCC2691AC1A28,518 Tags
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