N8251A

Overview

The N8251A is a Universal Synchronous/Asynchronous Receiver/Transmitter (USART) designed for data communications with microprocessor families such as MCS-48, 80, 85, and iAPX 86, 88. Fabricated using high-performance HMOS technology, it accepts parallel data characters from the CPU and converts them into a continuous serial data stream for transmission. Simultaneously, it receives serial data streams and converts them into parallel data characters for the CPU. The device signals the CPU when ready to accept new characters or upon character reception, allowing status reading including error detection and control signals like SYNDET and TxEMPTY.

Feature Summary

• Supports virtually any serial data transmission technique, including IBM bi-sync protocols.
• Provides bidirectional conversion between parallel CPU data and serial communication streams.
• Includes internal status signaling for transmission readiness and reception completion.

Applications

• Peripheral interface for Intel MCS-48 microprocessor systems.
• Data communication link for Intel 80 and 85 series processors.
• Serial I/O expansion for iAPX 86 and 88 microprocessor families.

Part Context

The N8251A is part of the 8251 USART family, originally developed by Intel Corporation. It serves as a standard programmable communication interface component for legacy microprocessor architectures. The device enables flexible serial communication configurations without requiring external logic gates for protocol handling, simplifying system design for embedded controllers and industrial applications utilizing these specific processor buses.

Replacement Considerations

Compatible alternatives include the Rochester Electronics 8251A in a 28-pin DIP package, Toshiba TMP82C51A, Dynex Semiconductor MA28151 for radiation-hardened environments, and InnovASIC IA8251. Verify pinout compatibility and voltage levels when substituting across manufacturers.