NXP Semiconductors SCC2681TC1A44,529

Overview

SCC2681TC1A44 from NXP Semiconductors (formerly Philips Semiconductors) is a dual-channel CMOS universal asynchronous receiver/transmitter (DUART) in 44-pin PLCC package, supporting independent full-duplex serial communication on two channels with programmable baud rates up to 115.2 kbaud, quadruple receiver buffering, and +5 V single-supply operation for industrial embedded control systems.

For engineers reviewing the SCC2681TC1A44 datasheet, SCC2681TC1A44 pinout, SCC2681TC1A44 application, or SCC2681TC1A44 equivalent, key selection considerations include its 44-pin PLCC footprint, dual-channel interrupt-driven I/O capability, 16-bit counter/timer, multipurpose I/O ports, and compatibility with legacy microprocessor buses requiring minimal wait states.

Technical Context

The SCC2681TC1A44 implements two independent UART channels sharing a common 8-bit bidirectional data bus, address decoding (A0–A3), and control signals (RDN, WRN, CEN). Each channel features separate receiver and transmitter shift registers, holding registers, status registers, and mode registers, enabling simultaneous asynchronous serial communication at different data formats and baud rates.

Its timing architecture integrates an on-chip crystal oscillator (X1/CLK, X2), external clock inputs for Rx/Tx (IP4–IP6, IP3, IP5), and a 16-bit programmable counter/timer used for baud rate generation or general-purpose timing. The device supports automatic echo, local/remote loopback, false start bit detection, line break handling, and multidrop wake-up mode via dedicated control logic and status flags.

Key Specifications

Pinout & Package

SCC2681TC1A44 is housed in a 44-pin plastic leaded chip carrier (PLCC, SOT187-2) with J-lead configuration, designed for surface-mount assembly and thermal reliability in industrial PCB environments.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SCC2681TC1A44, SCC2692BZ offers drop-in thermal and ESD upgrades while preserving software and layout; TL16C550CP trades I/O versatility and dual-channel autonomy for deeper FIFO buffering and x86 BIOS compatibility - neither matches the SCC2681TC1A44's integrated counter/timer, auto RS-485, or multidrop wake-up capabilities.

Availability

SCC2681TC1A44 is available at Aetrix Electronics and suitable for industrial automation, legacy terminal interfacing, and point-of-sale systems requiring stable component supply, long-lifecycle support, and proven interoperability with 8/16-bit microprocessors.

Supply support for SCC2681TC1A44 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 (formerly Philips Semiconductors) is a global leader in high-performance mixed-signal ICs, with expertise in connectivity, security, and automotive electronics.

The SCC2681 product line was developed for industrial and embedded communications, delivering robust dual UART functionality with integrated timing, I/O, and protocol features for resource-constrained microcontroller systems.

FAQ

What is the maximum baud rate supported by the SCC2681TC1A44?

The SCC2681TC1A44 supports standard baud rates up to 115.2 kbaud using its internal 16-bit counter/timer or external clock inputs. With a 3.6864 MHz crystal, it achieves precise 115.2 kbaud (16× oversampling). Non-standard rates are possible up to 115.2 kbaud via programmable divisor values, and external 1× or 16× clocks allow further flexibility. The SCC2681TC1A44 does not support rates above 115.2 kbaud in standard configurations.

Does the SCC2681TC1A44 support RS-485 half-duplex operation?

Yes, the SCC2681TC1A44 supports RS-485 half-duplex operation through its multipurpose output port. OP0–OP7 can be configured for automatic direction control: when enabled, the DUART asserts a transmit-enable signal synchronized with TxDA/TxDB activity, eliminating need for external transceiver control logic. This auto turn-around feature is programmable per channel and is documented in the SCC2681TC1A44 OPCR register settings.

Can both UART channels of the SCC2681TC1A44 operate at different baud rates simultaneously?

Yes, the SCC2681TC1A44 allows independent baud rate configuration for each channel. Each receiver and transmitter can select from 22 fixed rates, non-standard rates derived from the shared 16-bit counter/timer, or external 1×/16× clocks. This enables true dual-speed operation - for example, Channel A at 9600 baud for a modem and Channel B at 115.2 kbaud for a printer - without timing conflict or software overhead.

What is the function of the IP0–IP6 and OP0–OP7 pins on the SCC2681TC1A44?

IP0–IP6 (7-bit input port) and OP0–OP7 (8-bit output port) are programmable multifunction I/O resources. IP pins support clear-to-send inputs, external clock sources, or general-purpose sensing with change-of-state detection and internal pull-ups. OP pins serve as request-to-send outputs, clock outputs, interrupt flags (e.g., OP4 = RxRDYA), or general-purpose control signals with individual bit set/reset. Their functions are selected via OPCR and IPCR registers in the SCC2681TC1A44.

Is the SCC2681TC1A44 compatible with modern microcontrollers using 3.3 V I/O?

No, the SCC2681TC1A44 is a +5 V-only device with TTL/CMOS input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output drive levels referenced to VCC = +5 V. Direct connection to 3.3 V microcontrollers risks overvoltage damage to inputs and logic-level incompatibility on outputs. Level-shifting circuitry (e.g., TXB0108 or discrete MOSFET translators) is required for safe interfacing with 3.3 V systems. The SCC2681TC1A44 datasheet specifies no 3.3 V operation.