8251A/BXA

Overview

The Rochester Electronics 8251A/BXA is a Universal Synchronous/Asynchronous Receiver/Transmitter (USART) fabricated using high-performance HMOS technology. It serves as an industry-standard programmable communication interface designed for integration with microprocessor families including MCS-48, 80, 85, and iAPX 86, 88. The device accepts parallel data characters from the CPU and converts them into continuous serial streams for transmission. Conversely, it receives serial data streams and converts them back into parallel data characters for the CPU. The USART signals the CPU upon readiness to accept new transmission characters or upon receipt of received characters. Full status monitoring, including error detection and control signals like SYNDET and TxEMPTY, is available via CPU read access at any time.

Feature Summary

• Programmable serial data transmission techniques compatible with various standards
• Bidirectional conversion between parallel CPU data and serial communication streams
• Integrated status reporting for transmission errors and control signals

Applications

• Data communications peripherals for MCS-48, 80, and 85 microprocessors
• Serial interface modules for iAPX 86 and 88 processor families
• Systems requiring IBM bi-sync protocol support

Procurement Notes

Verify the specific lot traceability and wafer fabrication origin when sourcing from Rochester Electronics, as they provide redistribution services for end-of-life components. Confirm that the package marking matches the requested 8251A/BXA designation and check for any specific handling requirements associated with older HMOS technology devices. Ensure the component meets the required environmental specifications for the intended deployment environment.

Selection Notes

Select this component when a direct replacement for legacy Intel 8251A USART functionality is required in systems utilizing MCS or iAPX microprocessor architectures. It is suitable for designs needing synchronous or asynchronous serial communication capabilities without external controller logic. Consider the pinout compatibility with original equipment designs to minimize board layout changes during retrofitting or maintenance upgrades.

Part Context

Rochester Electronics specializes in the distribution of obsolete and hard-to-find integrated circuits, providing continuity for products no longer manufactured by original vendors. The 8251A/BXA represents their redistribution of the classic Intel USART, ensuring availability for industrial, aerospace, and defense applications where long-term supply stability is critical. This part maintains the functional integrity of the original specification while being sourced through authorized secondary channels.

Replacement Considerations

The Toshiba TMP82C51A offers functional compatibility as a programmable communication interface. For radiation-hardened environments, the Dynex Semiconductor MA28151 provides a robust alternative. InnovASIC's IA8251 is another potential substitute for standard USART applications.