DESCRIPTION
The DS2251T is an 8051 compatible microcontroller module based on nonvolatile RAM technology. It is designed for systems that need large quantities of nonvolatile memory. Like other members of the Secure Microcontroller family, it provides full compatibility with the 8051 instruction set, timers, serial port, and parallel I/O ports. By using NVRAM instead of ROM, the user can program, then reprogram the microcontroller while in–system. The application software can even change its own operation. This allows frequent software upgrades, adaptive programs, customized systems, etc. In addition, by using NVRAM, the DS2251T is ideal for data logging applications. The powerful real time clock includes interrupts for time stamp and date. It keeps time to one hundredth of second using its on– board 32 KHz crystal.

FEATURES
• 8051 compatible microcontroller adapts to its task
    – 32K, 64K, or 128K bytes of nonvolatile SRAM for program and/or data storage
    – In–system programming via on–chip serial port
    – Capable of modifying its own program or data memory in the end system
    – Provides separate Byte–wide bus for peripherals
    – Performs CRC–16 check of NVRAM memory
• High–reliability Operation
    – Maintains all nonvolatile resources for over 10 years in the absence of power
    – Power–fail reset
    – Early Warning Power–fail Interrupt
    – Watchdog Timer
    – Lithium backed memory remembers system state
    – Precision reference for power monitor
• Fully 8051 Compatible
    – 128 bytes scratchpad RAM
    – Two timer/counters
    – On–chip serial port
    – 32 parallel I/O port pins
• Permanently powered real time clock