Texas Instruments TL16C450N

Overview

TL16C450N from Texas Instruments is a CMOS asynchronous communications element (ACE) functioning as a UART interface in microcomputer systems. It performs serial-to-parallel and parallel-to-serial conversion, supports programmable baud rates up to 256 kbit/s, features full double buffering, and implements standard start/stop/parity framing for RS-232 communication links.

For engineers reviewing the TL16C450N datasheet, TL16C450N pinout, TL16C450N application, or TL16C450N equivalent, key selection criteria include its 40-pin FN/DIP package, independent receiver clock input, fully prioritized interrupt system, 8-bit bidirectional data bus with 3-state TTL drive, and compatibility with legacy NS16C450-based designs.

Technical Context

The TL16C450N integrates a 16× baud rate generator dividing reference clocks by divisors from 1 to 65535, producing BAUDOUT for transmitter timing and supporting RCLK-driven receiver sampling. Its register set includes divisor latches (LSB/MSB), line control/status, modem control/status, and interrupt enable/identification registers accessed via A0–A2 address lines and DOSTR/DISTR strobes.

It implements full modem control (RTS/CTS/DTR/DSR/RI/DCD), loopback diagnostics, false start bit detection, and line break generation/detection. The device uses master reset (MR) to initialize registers and outputs, and supports both polled and hardware-prioritized interrupt handling with four priority levels: receiver line status (highest), received data available, transmitter holding register empty, and modem status (lowest).

Key Specifications

Pinout & Package

The TL16C450N is available in a 40-pin plastic DIP (N package) and a 44-pin plastic quad flat pack (FN package); the N package was obsoleted as of July 30, 2006. This page documents the FN package pinout per Texas Instruments SLLS037C (Rev. January 2006).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL16C450N, TL16C550C adds FIFO buffering and deeper interrupt management but requires firmware updates, while MAX3232E serves only as a physical-layer driver and cannot perform UART functions - making TL16C450N irreplaceable for standalone serial protocol handling in resource-constrained systems.

Availability

TL16C450N is available at Aetrix Electronics and suitable for industrial serial gateways, legacy PC communication cards, point-of-sale terminal interfaces, and medical device data loggers requiring stable component supply and long-term design continuity.

Supply support for TL16C450N 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The TL16C450N belongs to TI's legacy communications interface product line, designed specifically to provide pin- and software-compatible UART functionality for industrial control, embedded computing, and retro-compatibility applications.

FAQ

What is the maximum baud rate supported by the TL16C450N?

The TL16C450N supports baud rates from DC up to 256 kbit/s. This maximum is achieved using a 4.096 MHz crystal with a divisor of 1, generating a 16× clock of 65.536 MHz internally scaled to produce the serial bit stream. The device maintains timing accuracy across this range under recommended operating conditions (VCC = 4.75–5.25 V, TA = 0–70°C). TL16C450N's baud generator accepts divisors from 1 to 65535, allowing fine-grained rate selection for legacy and custom protocols.

Does the TL16C450N support hardware flow control?

Yes, the TL16C450N fully supports hardware flow control via RTS/CTS signals. The RTS (Request to Send) output is controlled by bit 1 of the Modem Control Register (MCR), and the CTS (Clear to Send) input is monitored in the Modem Status Register (MSR). When CTS transitions, the TL16C450N can generate a modem status interrupt if enabled. This allows real-time throttling of transmission without CPU polling. TL16C450N also supports DTR/DSR for device readiness signaling, making it suitable for full RS-232 handshaking implementations.

How does the TL16C450N handle interrupt prioritization?

The TL16C450N implements a fixed 4-level hardware interrupt priority scheme: (1) receiver line status (overrun, parity, framing errors, break), (2) received data available, (3) transmitter holding register empty, and (4) modem status changes. The Interrupt Identification Register (IIR) reports the highest-pending interrupt type via bits 1–2, while bit 0 indicates interrupt pending. This prioritization ensures critical error conditions preempt less urgent events like transmit completion. TL16C450N's interrupt structure requires no software arbitration, reducing latency in time-sensitive serial applications.

Can the TL16C450N operate with an external clock source instead of a crystal?

Yes, the TL16C450N accepts an external clock source on XTAL1, with XTAL2 left unconnected or grounded. The device's internal oscillator circuitry supports clock inputs up to 9 MHz, eliminating the need for a crystal. When using an external clock, the same baud rate generation and timing specifications apply. This configuration simplifies board layout and improves startup reliability in systems where crystal oscillation stability is a concern. TL16C450N's clock input tolerance and drive strength are specified for TTL/CMOS-level signals, ensuring compatibility with common clock generators.

What is the function of the DDIS pin on the TL16C450N?

The DDIS (Driver Disable) pin is an active-high output that controls external transceivers. When the TL16C450N is not reading data (i.e., during write cycles or idle states), DDIS goes high to disable the external RS-232 driver, preventing bus contention on shared lines. This feature enables clean integration with half-duplex or bidirectional level shifters like the MAX232 family. DDIS timing is synchronized to internal read strobes (DISTR), ensuring glitch-free control. TL16C450N's DDIS eliminates the need for additional logic to manage transceiver direction, simplifying interface design.