NXP Semiconductors SC26C92A1B,551

Overview

SC26C92A1B,551 from NXP Semiconductors (formerly Philips) is a dual-channel CMOS universal asynchronous receiver/transmitter (DUART) IC designed for microprocessor-based serial communications systems. It provides two independent full-duplex UART channels with 8-character transmit and receive FIFOs, programmable baud rates up to 230.4 kbaud, and integrated crystal oscillator - used in industrial terminal controllers, legacy POS systems, and embedded modem interfaces.

For engineers reviewing the SC26C92A1B,551 datasheet, SC26C92A1B,551 pinout, SC26C92A1B,551 application, or SC26C92A1B,551 equivalent, key selection considerations include its 44-pin PQFP package, dual-channel independent clocking, receiver watchdog timers, RTS/CTS flow control support, and compatibility with SCC2692/SCN2681 legacy designs.

Technical Context

The SC26C92A1B,551 implements two independent UART channels sharing a common 8-bit bidirectional data bus, address decoding (A0–A3), and interrupt architecture. Each channel features separate programmable baud rate generators - selectable from 27 fixed rates (50–230.4 kbaud), 16× clock derived from an internal 16-bit counter/timer, or external 1×/16× clock inputs - enabling true dual-speed operation for clustered terminal or multidrop applications.

Its timing subsystem integrates an on-chip crystal oscillator (X1/CLK, X2), a 16-bit counter/timer supporting timer, counter, and timeout modes, and four clock selectors that independently route timing sources to each receiver and transmitter. The device supports automatic wake-up in multidrop mode via 9-bit addressing and includes dedicated change-of-state detection on four input port pins (IP0–IP3) for event-driven I/O monitoring.

Key Specifications

Pinout & Package

SC26C92A1B,551 is housed in a 44-pin plastic quad flat pack (PQFP) per SOT307-2, with 0.8 mm lead pitch and exposed thermal pad (not electrically connected). Pin 1 is located at top-left corner with index mark; pins numbered counterclockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SC26C92C1B, the SC26C92A1B,551 offers extended temperature resilience and identical functionality - making it the preferred choice for field-deployed equipment. Against SCN2681C1B, SC26C92A1B,551 delivers measurable throughput gains via FIFO buffering and robustness via receiver watchdogs, justifying firmware updates for new designs.

Availability

SC26C92A1B,551 is available at Aetrix Electronics and suitable for industrial terminal controllers, legacy point-of-sale systems, and embedded modem interfaces requiring stable component supply across extended product lifecycles.

Supply support for SC26C92A1B,551 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 design heritage.

The SC26C92A1B,551 belongs to NXP's legacy communications IC portfolio, engineered specifically for backward-compatible upgrades of 1980s–1990s serial infrastructure - emphasizing pin-and-function equivalence, industrial temperature operation, and minimal firmware migration effort.

FAQ

What is the maximum baud rate supported by SC26C92A1B,551?

The SC26C92A1B,551 supports a maximum baud rate of 230.4 kbaud in 16× mode using either the internal baud rate generator or the programmable counter/timer. This is achieved with a 3.6864 MHz crystal; external clock inputs must be scaled accordingly. The device does not support rates above 230.4 kbaud, and exceeding this limit may cause framing errors or data corruption.

Does SC26C92A1B,551 require an external crystal or can it use an external clock?

SC26C92A1B,551 supports both configurations: a 3.6864 MHz crystal connected between X1/CLK and X2, or an external TTL/CMOS-compatible clock signal applied to X1/CLK with X2 left open. The external clock must meet AC specifications - minimum 0.1 MHz, maximum 8 MHz, with 50 ns minimum high/low time - and must be present at all times for stable operation.

How does the receiver watchdog timer function in SC26C92A1B,551?

The SC26C92A1B,551 includes a dedicated watchdog timer for each receiver channel that triggers when no valid start bit is detected for a programmable timeout period. It asserts the corresponding RxRDY interrupt and sets the timeout status bit in the status register. This feature helps detect broken connections or stuck lines in multidrop or long-cable installations without CPU polling.

Can SC26C92A1B,551 operate with different baud rates on Channel A and Channel B simultaneously?

Yes - SC26C92A1B,551 allows fully independent baud rate configuration per channel. Each receiver and transmitter can select timing from the baud rate generator, counter/timer, or external 1×/16× clock via dedicated clock selector registers. This enables true dual-speed operation, such as 9600 baud for a host link and 115.2 kbaud for a local printer, without shared timing constraints.

Is SC26C92A1B,551 pin-compatible with the older SCC2692?

Yes - SC26C92A1B,551 is explicitly specified as a pin-and-function replacement for the SCC2692, with identical pinout, register map, and power-up behavior. Key enhancements - including deeper FIFOs, watchdog timers, and extended baud rates - are implemented without altering physical or logical interface compatibility, enabling direct substitution in existing PCB layouts.