DESCRIPTION
The DS2251T 128k soft microcontroller module 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 NV RAM 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 NV RAM, the DS2251T is ideal for data logging applications. The powerful realtime clock includes interrupts for time stamp and date. It keeps time to one-hundredth of seconds using its on-board 32kHz crystal.

FEATURES
■ 8051-Compatible Microcontroller Adapts to Its Task
    32, 64, or 128kbytes 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 NV RAM Memory
■ High-Reliability Operation
    Maintains All Nonvolatile Resources Up to 10 Years in the Absence of VCC at Room Temperature
    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