NXP Semiconductors SCC2681AE1A44,512

Overview

SCC2681AE1A44 from NXP Semiconductors (formerly Philips) is an industrial-grade dual asynchronous receiver/transmitter (DUART) IC providing two independent full-duplex UART channels in a 44-pin PLCC package. It operates from a single +5 V ±10% supply, supports 5–8 data bits with programmable parity and stop bits, delivers up to 115.2 kbaud per channel, and integrates a 16-bit counter/timer and dual multipurpose I/O ports - used in legacy industrial control systems requiring RS-232/422 serial communication with deterministic timing.

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), quadruple-receiver buffering for low-interrupt overhead, independent baud rate programming per channel (including crystal-based or external clock options), and open-drain interrupt outputs configurable via OP4–OP7.

Technical Context

The SCC2681AE1A44 implements two fully independent UART channels (A and B), each with separate programmable baud rate generators selecting from 22 fixed rates (50–115.2 kbaud), 16× clock derived from a shared 16-bit counter/timer, or external 1×/16× clock inputs. Its timing architecture includes an on-chip crystal oscillator (3.6864 MHz nominal) and four clock selectors enabling asymmetric receiver/transmitter speeds - critical for clustered terminal or multidrop applications.

It features a single active-low interrupt output (INTRN) with eight maskable sources, plus optional discrete interrupt routing via OP3–OP7 (e.g., RxRDY, TxRDY, C/T interrupt). The 7-bit input port (IP0–IP6) supports change-of-state detection on four pins with internal 1–4 µA pull-ups, while the 8-bit output port (OP0–OP7) offers individual bit set/reset and function assignment (RTS, DMA, auto 485 turn-around) under register control.

Key Specifications

Pinout & Package

SCC2681AE1A44 is housed in a 44-pin plastic leaded chip carrier (PLCC) package (SOT187-2), with 0.050" lead pitch and index corner marking. The package supports reflow soldering and provides mechanical stability for industrial board-level assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SCC2692AE1A44, the SCC2681AE1A44 lacks enhanced ESD protection but retains full compatibility with legacy 5 V industrial buses; compared with TL16C2550IPN, it avoids 3.3 V conversion and external clock dependencies but trades FIFO depth for deterministic interrupt latency in time-critical polling loops.

Availability

SCC2681AE1A44 is available at Aetrix Electronics and suitable for industrial automation, legacy terminal interfacing, and medical data acquisition systems requiring stable component supply across long production 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.

The SCC2681 series was designed specifically for robust, long-lifecycle serial communication in industrial control and legacy infrastructure - emphasizing deterministic timing, wide temperature operation, and minimal external component count.

FAQ

What is the maximum baud rate supported by the SCC2681AE1A44?

The SCC2681AE1A44 supports a maximum baud rate of 115.2 kbaud per channel. This rate is achieved using the internal baud rate generator with a 3.6864 MHz crystal or external clock. The device also allows non-standard rates up to 115.2 kbaud via its 16-bit programmable counter/timer, making the SCC2681AE1A44 suitable for both standard and proprietary serial protocols in industrial settings.

Does the SCC2681AE1A44 require an external crystal oscillator?

No, the SCC2681AE1A44 includes an on-chip crystal oscillator and can operate directly with a 3.6864 MHz crystal connected between X1/CLK and X2 pins. Alternatively, an external clock signal within 1.0–4.0 MHz may be applied to X1/CLK, with X2 left unconnected. This flexibility eliminates the need for external oscillator circuitry in the SCC2681AE1A44 design, reducing BOM cost and board space.

How does the SCC2681AE1A44 handle flow control between UART channels?

The SCC2681AE1A44 implements hardware flow control using its multipurpose I/O ports: OP0 and OP1 serve as active-low RTS outputs for Channels A and B, while IP0 and IP1 function as active-low CTS inputs. When CTS is asserted, transmission halts after the current character; deassertion resumes transmission. This handshake is managed entirely in hardware, ensuring reliable inter-device synchronization without CPU intervention in the SCC2681AE1A44.

Can the SCC2681AE1A44 operate in a multidrop network with automatic wake-up?

Yes, the SCC2681AE1A44 supports automatic wake-up mode for multidrop applications. When enabled, it detects break conditions (long LOW pulses) on either RXDA or RXDB and asserts INTRN to wake the host CPU - even from low-power states. This feature is essential for energy-efficient polling architectures in point-of-sale or building automation networks where the SCC2681AE1A44 acts as a central serial hub.

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 clocks). Four pins (IP0–IP3) support change-of-state detection with interrupt capability, enabling hardware-triggered responses to switch closures or sensor edges. Each pin includes a 1–4 µA internal pull-up, eliminating external resistors - a key design simplification in the SCC2681AE1A44 for industrial I/O expansion.