NXP Semiconductors SCC2691AE1A28,518

Overview

SCC2691AE1A28 from NXP Semiconductors (formerly Philips Semiconductors) is a CMOS-LSI universal asynchronous receiver/transmitter (UART) with full-duplex serial communication, quadruple-buffered receiver FIFO, independent receiver/transmitter baud rate selection, and integrated 16-bit counter/timer. It operates from a single +5V supply and supports industrial temperature range (–40°C to +85°C) in 28-pin PLCC package.

For engineers reviewing the SCC2691AE1A28 datasheet, SCC2691AE1A28 pinout, SCC2691AE1A28 application, or SCC2691AE1A28 equivalent, key selection criteria include dual-speed channel support, programmable data format (5–8 bits, parity options, 1/1.5/2 stop bits), false start bit detection, line break handling, and power-down mode with register retention.

Technical Context

The SCC2691AE1A28 implements a fully programmable UART architecture with independent clock selectors for receiver and transmitter, enabling true dual-speed operation-e.g., 9600 baud receive / 115.2 kbaud transmit. Its 16-bit counter/timer serves both as baud rate source and general-purpose timing resource, configurable via auxiliary control register (ACR) for output on MPO pin.

Receiver logic includes quadruple buffering (3-character FIFO + shift register), automatic RTS flow control based on FIFO full status, and address/data frame recognition for multi-processor wake-up. Transmitter supports break generation, automatic echo, local/remote loopback, and marking-state idle output-all under software control via command and mode registers.

Key Specifications

Pinout & Package

SCC2691AE1A28 is housed in a 28-pin PLCC (SOT261-2) package with J-lead configuration, 1.27 mm pitch, and body size 11.5 × 11.5 mm. Pin 1 is located at the index corner adjacent to the notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SCC2691AE1A28, SCC2692AE1A28 offers scalable performance within identical mechanical and electrical constraints, while TL16C550CPTR trades specialized features for broad software ecosystem support-making the former ideal for custom embedded control and the latter for standardized PC-architecture integration.

Availability

SCC2691AE1A28 is available at Aetrix Electronics and suitable for industrial terminal systems, multi-processor communication nodes, and legacy equipment interface adapters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SCC2691AE1A28 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 SCC2691 family was designed for robust, low-power asynchronous serial communication in industrial control and clustered terminal systems-emphasizing dual-speed flexibility, hardware flow control, and extended temperature reliability.

FAQ

What is the maximum supported baud rate for SCC2691AE1A28?

The SCC2691AE1A28 supports up to 115.2 kbaud using its internal baud rate generator or counter/timer. When driven by an external 16X clock, it can achieve non-standard rates up to 115.2 kbaud; the device does not support rates beyond this limit per its datasheet specifications. The SCC2691AE1A28's clock selector architecture allows independent configuration for receiver and transmitter, enabling asymmetric operation within this bound.

Does SCC2691AE1A28 support automatic hardware flow control?

Yes, the SCC2691AE1A28 supports automatic RTS flow control via its MPO pin. When configured as RTSN, the output is automatically negated when the 3-character receiver FIFO becomes full and reasserted when space becomes available-enabling real-time overrun prevention without CPU intervention. This behavior is enabled through mode register programming and requires no firmware polling or interrupt servicing.

Can SCC2691AE1A28 operate with an external clock instead of a crystal?

Yes, the SCC2691AE1A28 accepts an external clock signal on the X1/CLK pin, eliminating the need for a crystal. The external clock must be 0–4 MHz, TTL-compatible, and meet specified voltage thresholds (VIL ≤ 0.8 V, VIH ≥ 0.8VCC). When using external clocking, X2 may be left unconnected or grounded. The SCC2691AE1A28 uses this clock directly for its baud rate generator, counter/timer, and internal timing circuits.

What is the receiver FIFO depth of SCC2691AE1A28?

The SCC2691AE1A28 features a quadruple-buffered receiver architecture consisting of a 3-character first-in-first-out (FIFO) queue plus one additional character in the shift register-totaling four stages of buffering. This design significantly reduces the risk of receiver overrun and lowers interrupt overhead in CPU-driven systems. The FFULL status bit asserts when all three FIFO positions are occupied, and RxRDY indicates at least one character is ready for read.

Is SCC2691AE1A28 compatible with the TL16C550 UART register set?

No, the SCC2691AE1A28 uses a proprietary register map distinct from the industry-standard TL16C550. Its address decoding (A0–A2), register layout (MR1/MR2, CSR, ACR, CTUR/CTLR), and interrupt handling differ fundamentally. Firmware written for TL16C550 will not operate correctly on SCC2691AE1A28 without complete register-level reimplementation. The SCC2691AE1A28 is optimized for dual-speed and multi-processor applications-not PC BIOS compatibility.