Analog Devices Inc./Maxim Integrated DS2251T-128-16

Overview

DS2251T-128-16 from Maxim Integrated is an 8051-compatible soft microcontroller module with 128kB nonvolatile SRAM, 16MHz crystal support, and permanently powered real-time clock (RTC) accurate to 0.01s using an onboard 32kHz crystal. It delivers in-system reprogrammability, CRC-16 memory integrity checking, and lithium-backed state retention for data logging and adaptive firmware applications.

For engineers reviewing the DS2251T-128-16 datasheet, DS2251T-128-16 pinout, DS2251T-128-16 application, or DS2251T-128-16 equivalent, key selection criteria include byte-wide non-multiplexed address/data bus (BA13–BA0 / BD7–BD0), power-fail interrupt/reset capability, RTC interrupt outputs (INTA/INTB/INTP), VRST and PF status signaling, and partitionable NV RAM memory mapping.

Technical Context

The DS2251T-128-16 implements a full 8051 instruction set with two timer/counters, on-chip UART, and 32 parallel I/O pins. Its memory architecture supports dynamic partitioning between program and data segments via SFR-controlled PM and PES bits, enabling runtime reconfiguration of 64k address space.

Power management integrates three voltage thresholds: VPFW (4.25–4.50V) for early-warning interrupt, VCCMIN (4.00–4.25V) for reset activation, and VLI for lithium switchover. The RTC operates independently under battery backup and provides programmable SQW output and three interrupt sources tied to time/date events.

Key Specifications

Pinout & Package

DS2251T-128-16 uses a 72-pin SIMM package with 0.050" lead pitch and mechanical dimensions of 4.25" × 1.00". The module features dual-row edge-connectors compatible with standard SIMM sockets and includes dedicated lithium cell integration for nonvolatile operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microcontroller-with-NV-memory applications.

Compared with DS2251T-64-16 and DS2251T-32-16, the DS2251T-128-16 provides double and quadruple NV SRAM capacity respectively-enabling longer data logging intervals, larger adaptive firmware images, or segregated program/data partitions without sacrificing 8051 compatibility, RTC functionality, or power-fail resilience.

Availability

DS2251T-128-16 is available at Aetrix Electronics and suitable for industrial data loggers, secure utility meters, adaptive controllers, and legacy system retrofits requiring stable component supply, long-term lifecycle support, and guaranteed nonvolatile memory retention.

Supply support for DS2251T-128-16 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

Maxim Integrated (now part of Analog Devices) designs high-reliability analog and mixed-signal ICs for industrial, automotive, and communications applications.

The DS2251T-128-16 belongs to Maxim's Secure Microcontroller family, engineered for systems demanding nonvolatile program/data storage, autonomous power-loss response, and tamper-resilient timekeeping in harsh or unattended environments.

FAQ

What is the maximum crystal frequency supported by DS2251T-128-16?

The DS2251T-128-16 supports a maximum crystal frequency of 16MHz, as confirmed in the Ordering Information table and AC Characteristics section. This enables full-speed 8051 execution at 2 million instructions per second (MIPS), with timing parameters validated specifically at 16MHz in the datasheet's expanded bus and serial port timing tables.

Does DS2251T-128-16 include an integrated real-time clock?

Yes, DS2251T-128-16 integrates a permanently powered real-time clock (RTC) with 0.01-second resolution, driven by an onboard 32kHz crystal. It provides three interrupt outputs (INTA, INTB, INTP), a programmable square-wave output (SQW), and maintains timekeeping during VCC loss via lithium backup-fully documented in the Description and Pin Description sections.

How does DS2251T-128-16 handle power failure events?

DS2251T-128-16 implements three-tier power monitoring: VPFW (4.25–4.50V) triggers an early-warning interrupt, VCCMIN (4.00–4.25V) asserts reset, and VLI (~3.0–3.3V) switches to lithium backup. The VRST and PF pins provide hardware-level status signaling, and all nonvolatile resources-including RTC and NV SRAM-are retained for ≥10 years at room temperature with zero VCC.

Can DS2251T-128-16 reprogram its own firmware in the field?

Yes, DS2251T-128-16 supports in-system programming via its on-chip serial bootstrap loader. The application firmware can modify its own program or data memory in the end system, enabling field upgrades, adaptive behavior, and customized configurations-all without removing the module from the host system.

What is the memory architecture of DS2251T-128-16?

DS2251T-128-16 uses 128kB of nonvolatile SRAM with dynamic partitioning capability: users can allocate portions as write-protected program memory (ROM-emulation) or read/write data memory via Special Function Registers. Memory access occurs through a non-multiplexed byte-wide bus (BA13–BA0 / BD7–BD0), preserving all 32 I/O pins for application use.