NXP Semiconductors SCC2691AE1A28,512

Overview

SCC2691AE1A28 from NXP Semiconductors (formerly Philips Semiconductors) is a CMOS-LSI universal asynchronous receiver/transmitter (UART) with full-duplex operation, quadruple-buffered receiver FIFO, and independent programmable baud rate generation for transmitter and receiver. It supports 5–8 data bits, odd/even/no parity, 1/1.5/2 stop bits, and operates at +5 V over –40°C to +85°C. Used in industrial serial communication interfaces requiring dual-speed channel support and low-power operation.

For engineers reviewing the SCC2691AE1A28 datasheet, SCC2691AE1A28 pinout, SCC2691AE1A28 application, or SCC2691AE1A28 equivalent, key selection criteria include its 28-pin PLCC package, TTL-compatible 8-bit parallel bus interface, independent 16-bit counter/timer, crystal oscillator integration, and support for automatic RTS flow control via MPI/MPO handshaking.

Technical Context

The SCC2691AE1A28 implements a fully synchronous internal timing architecture with an on-chip crystal oscillator (3.6864 MHz nominal), dual-path baud rate selection (18 fixed rates up to 115.2 kbaud plus user-defined via 16-bit counter/timer), and independent clock selectors for Rx and Tx paths. Its receiver uses 16X oversampling with false start bit detection and break condition handling.

It features a three-level deep FIFO with RxRDY/FFULL status signaling, programmable channel modes (normal, auto-echo, local/remote loopback), and seven maskable interrupt sources routed to a single open-drain INTRN output. The auxiliary control register (ACR) enables dynamic reconfiguration of MPO as RTSN, TxC1X/TxC16X, RxC1X/RxC16X, C/TO, TxRDY, or RxRDY/FFULL.

Key Specifications

Pinout & Package

SCC2691AE1A28 is housed in a 28-pin Plastic Leaded Chip Carrier (PLCC) package per SOT261-2, with J-lead configuration, 1.27 mm pitch, and exposed pad not present. Pin functions are validated per Philips Semiconductors datasheet SD00122 (2006 Aug 04).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SCC2691AE1A28, SCC2692AE1A28 delivers marginally improved receive buffering without layout impact, while SC16C2552BIBS,112 provides dual-channel flexibility at the cost of footprint and pin-count increase - both retain identical register-level programming and industrial temperature qualification.

Availability

SCC2691AE1A28 is available at Aetrix Electronics and suitable for industrial automation, motor control systems, and legacy terminal interface designs 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' analog and mixed-signal heritage.

The SCC2691 product line was designed for robust, low-power asynchronous serial communication in harsh industrial environments, emphasizing register compatibility, hardware flow control, and long-term supply stability for legacy infrastructure upgrades.

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 external 16X clock input. Non-standard rates are achievable via the 16-bit counter/timer, with timing constraints limiting practical operation to ≤115.2 kbaud under standard 3.6864 MHz crystal drive. The SCC2691AE1A28 datasheet confirms this limit in AC Electrical Characteristics (fRX/fTX = 2.0 MHz max for 16X mode).

Does SCC2691AE1A28 support automatic hardware flow control?

Yes, the SCC2691AE1A28 supports automatic RTS/CTS flow control through its MPI and MPO pins. When configured via the auxiliary control register, MPO outputs RTSN, and MPI accepts CTSN; the UART automatically negates RTSN when the 3-character receiver FIFO is full and reasserts it upon space availability. This behavior is documented in the "Receiver" section of the SCC2691AE1A28 datasheet.

What is the function of the A0–A2 pins on SCC2691AE1A28?

The A0–A2 pins on SCC2691AE1A28 serve as a 3-bit register address decoder, selecting one of eight internal register groups during CPU read/write cycles. Valid combinations include MR1/MR2 (mode registers), SR/CSR (status/clock select), RHR/THR (receive/transmit holding registers), ISR/IMR (interrupt status/mask), and CTU/CTUR (counter/timer upper registers). This mapping is defined in Table 1 of the SCC2691AE1A28 datasheet.

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

Yes, the SCC2691AE1A28 can operate with an external clock applied to the X1/CLK pin, eliminating the need for a crystal. The X2 pin may be left unconnected or grounded. The device accepts 0–4 MHz logic-level clock inputs, and all internal timing-including baud generation, counter/timer, and sampling-is derived from this source. This is explicitly permitted in the "Clock Timing" section of the SCC2691AE1A28 datasheet.

What is the power consumption of SCC2691AE1A28 in power-down mode?

In power-down mode, the SCC2691AE1A28 freezes its internal oscillator while retaining all register contents, reducing supply current to ≤500 µA over the full –40°C to +85°C industrial temperature range. This value is specified in the DC Electrical Characteristics table under ICCD (power-down current) in the official SCC2691AE1A28 datasheet.