NXP Semiconductors SCC2681AE1A44,518

Overview

SCC2681AE1A44 from NXP Semiconductors (formerly Philips) is an industrial-grade dual universal asynchronous receiver/transmitter (DUART) IC providing two independent full-duplex serial channels in a 44-pin PLCC package. It supports programmable data formats (5–8 data bits, odd/even/no parity, 1/1.5/2 stop bits), 22 fixed baud rates up to 115.2 kbaud, and independent Rx/Tx clock selection via on-chip crystal oscillator (3.6864 MHz), programmable 16-bit counter/timer, or external 1×/16× clocks. It is used in legacy industrial control systems requiring robust RS-232/422/485 interface expansion with hardware flow control and interrupt-driven I/O.

For engineers reviewing the SCC2681AE1A44 datasheet, SCC2681AE1A44 pinout, SCC2681AE1A44 application, or SCC2681AE1A44 equivalent, key selection considerations include its industrial temperature range (–40 °C to +85 °C), 44-pin PLCC package with 7-bit input port and 8-bit output port, quadruple receiver buffering, automatic RTS/CTS handshaking, and support for multidrop wake-up mode - all critical for deterministic serial communication in embedded automation and telecom infrastructure.

Technical Context

The SCC2681AE1A44 integrates two independent UART channels sharing a single 8-bit bidirectional data bus (D0–D7), address decoding (A0–A3), and chip enable (CEN) logic. Each channel features separate baud rate generators with selectable 16× or 1× clock outputs, enabling dual-speed operation - e.g., Channel A at 9600 baud for local console, Channel B at 115.2 kbaud for high-speed modem link.

Its timing subsystem includes an on-chip crystal oscillator (X1/CLK, X2), a 16-bit programmable counter/timer with three operating modes (timer, counter, timeout), and four clock selectors that route timing sources independently to each Rx/Tx path. The interrupt system uses a single active-low open-drain INTRN output with eight maskable conditions and optional discrete interrupt routing via OP3–OP7 pins for DMA-ready or TxRDY/RxRDY signaling.

Key Specifications

Pinout & Package

SCC2681AE1A44 is housed in a 44-pin plastic leaded chip carrier (PLCC44, SOT187-2) with J-lead configuration, suitable for surface-mount assembly and socketed prototyping. Pin 1 is marked by index corner; leads are arranged in a square grid with 0.05-inch pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual UART applications.

Compared with SCC2691AE1A44 and TL16C550CPTR, the SCC2681AE1A44 uniquely combines industrial temperature rating, on-chip oscillator, programmable counter/timer, and hardware flow control in a single PLCC package - making it optimal for cost-sensitive, space-constrained legacy upgrades where external clocking or FIFO expansion is unnecessary.

Availability

SCC2681AE1A44 is available at Aetrix Electronics and suitable for industrial automation, telecom infrastructure, and medical device manufacturing requiring stable component supply across extended product lifecycles.

Supply support for SCC2681AE1A44 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. Formerly Philips Semiconductors, it maintains legacy product support with full documentation and long-term availability commitments.

The SCC2681AE1A44 belongs to NXP's legacy communications IC portfolio, designed specifically for industrial serial interface expansion where reliability, deterministic timing, and backward compatibility with 8-bit microprocessor buses are essential.

FAQ

What is the maximum baud rate supported by the SCC2681AE1A44?

The SCC2681AE1A44 supports 22 fixed baud rates up to 115.2 kbaud. Its baud rate generator derives timing from the on-chip 3.6864 MHz crystal oscillator or external clock, producing 16× oversampled clocks. Non-standard rates can also be achieved using the programmable 16-bit counter/timer, allowing precise tuning within the same upper limit. This makes the SCC2681AE1A44 suitable for both legacy terminal interfaces and higher-speed modem links.

Does the SCC2681AE1A44 include an integrated crystal oscillator?

Yes, the SCC2681AE1A44 includes an on-chip crystal oscillator circuit. Pins X1/CLK and X2 are designed for direct connection to a 3.6864 MHz parallel-resonant crystal. When used, this eliminates the need for an external oscillator module or discrete inverter-based clock generator. The oscillator drives the baud rate generator, counter/timer, and internal logic - ensuring synchronous, jitter-free timing critical for error-free serial communication in the SCC2681AE1A44.

How does hardware flow control work on the SCC2681AE1A44?

Hardware flow control on the SCC2681AE1A44 is implemented via programmable RTS/CTS signals on OP0/OP1 (RTSAN/RTSBN) and IP0/IP1 (CTSAN/CTSBN). When enabled, the DUART automatically deasserts RTS upon receiver buffer fill and halts transmission when CTS goes HIGH. These pins support auto 485 turn-around and can be configured as open-drain outputs requiring external pull-ups. This ensures deterministic, zero-software-overhead handshaking - a core capability of the SCC2681AE1A44 in industrial serial networks.

Can the SCC2681AE1A44 operate with a single +5 V supply?

Yes, the SCC2681AE1A44 operates from a single +5 V ± 10% supply (VCC = Pin 44, GND = Pin 22). Its CMOS process ensures low power consumption (ICC ≤ 10 mA typical), and all I/O pins are 5 V tolerant with defined VIH/VIL thresholds. This simplifies power design in legacy systems using standard 5 V rails and avoids level-shifting components - a key advantage of the SCC2681AE1A44 in retrofit and industrial control applications.

What is the purpose of the 7-bit input port (IP0–IP6) on the SCC2681AE1A44?

The 7-bit input port (IP0–IP6) on the SCC2681AE1A44 serves dual roles: as general-purpose digital inputs or as dedicated control signals (e.g., CTS, external clock, TxCA/RxCA). IP0–IP3 feature change-of-state detection with interrupt capability, enabling hardware-triggered responses to front-panel switches or sensor edges. All inputs include internal 1–4 µA pull-up resistors, eliminating external biasing. This integrated flexibility reduces external component count and enhances real-time responsiveness - a defining feature of the SCC2681AE1A44 in embedded control.