NXP SCC2681AC1A44: A Comprehensive Technical Overview of the Dual Channel UART
The NXP SCC2681AC1A44 stands as a significant component in the landscape of legacy interface ICs, representing a highly integrated Dual Universal Asynchronous Receiver/Transmitter (UART) designed for demanding industrial and communications applications. This device encapsulates two independent full-duplex UART channels, providing a robust and flexible solution for serial data communication.
At its core, each channel of the SCC2681AC1A44 is functionally equivalent to the industry-standard PC16552D UART, ensuring software compatibility and ease of integration into existing designs. Each channel is capable of handling serial data rates up to 1.5 Mbps, making it suitable for a wide range of speed requirements, from slow modem links to high-speed data acquisition systems. A key feature is its on-chip programmable baud rate generator for each channel, which derives its clock from a single external crystal input, simplifying board design and reducing component count.
The programmability of the SCC2681AC1A44 is one of its greatest strengths. Key operational parameters can be set by software, including character length (5, 6, 7, or 8 bits), number of stop bits (1, 1.5, or 2), and parity (even, odd, or no parity). This flexibility allows it to interface with a vast array of serial devices, from old terminals to modern sensors. Furthermore, it features multi-purpose 16-byte FIFOs (First-In, First-Out buffers) for both transmitter and receiver on each channel. These FIFOs dramatically reduce the CPU overhead required for interrupt servicing by minimizing the number of interrupts generated during data transfers, thus enhancing overall system efficiency.
Beyond basic data handling, the SCC2681AC1A44 includes comprehensive modem control and handshake capabilities. Each channel provides full modem control signals (RTS, CTS, DSR, DTR, RI, DCD), enabling seamless interfacing with modems and other data communication equipment. Its interrupt system is highly sophisticated, prioritizing and identifying multiple interrupt sources to streamline the service routine of the host processor.
Housed in a 44-pin PLCC package, the device is designed for reliability and is characterized for extended industrial temperature ranges, ensuring stable operation in harsh environments. It operates from a single +5V power supply, a common standard in the embedded systems for which it was designed.
ICGOOODFIND: The NXP SCC2681AC1A44 is a quintessential dual UART that excels in reducing CPU overhead through its deep FIFOs and intelligent interrupt handling. Its high degree of programmability and comprehensive modem control make it an exceptionally versatile communications peripheral. While newer solutions exist, its robustness and proven architecture cement its status as a reliable workhorse for complex serial data routing tasks.
Keywords: Dual UART, FIFO Buffers, Programmable Baud Rate, Modem Control, Serial Communication.
