Analog Devices Inc./Maxim Integrated DS87C520-WCL

Overview

DS87C520-WCL from Maxim Integrated is a high-speed, 8051-compatible microcontroller in a 40-pin windowed CERDIP package, featuring a 4-clock-per-machine-cycle core, 16kB on-chip EPROM, 1kB MOVX-accessible SRAM, and dual hardware serial ports. It operates up to 33MHz with single-cycle instruction execution in 121ns and supports dynamic ROMSIZE configuration for boot-from-external-Flash applications.

For engineers reviewing the DS87C520-WCL datasheet, DS87C520-WCL pinout, DS87C520-WCL application, or DS87C520-WCL equivalent, key selection considerations include its 33MHz max clock, windowed CERDIP package for UV-erasable EPROM reprogramming, ROMSIZE register control for memory mapping flexibility, and dual DPTR support for accelerated block memory moves.

Technical Context

The DS87C520-WCL implements a redesigned 8051 core eliminating dummy memory cycles, achieving 2.5× average speedup over standard 8051 at identical crystal frequency. Its instruction timing differs from legacy 8051 - e.g., MOVX A,@DPTR executes in 2 machine cycles (8 clocks) vs. 24 clocks in original - while maintaining full 8051 instruction set compatibility and default 12-clock timer operation for backward timing alignment.

It integrates two full-duplex UARTs (Serial Port 0 on P3.0/P3.1, Serial Port 1 on P1.2/P1.3), programmable Power Management Mode (PMM) with 64×/1024× clock division, EMI-reduction ALE disable, and 13 interrupt sources including six external interrupts with configurable edge detection on P1.4–P1.7 and P3.2–P3.3.

Key Specifications

Pinout & Package

DS87C520-WCL is housed in a 40-pin windowed ceramic DIP (CERDIP) package, compatible with standard 8051 sockets and supporting UV erasure of on-chip EPROM. Pin functions follow industry-standard 8051 assignment with enhancements for dual serial ports and expanded interrupt capability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microcontroller applications.

Compared with DS87C520-MCL and DS83C520-MCL, the DS87C520-WCL uniquely supports UV-erasable EPROM reprogramming via its ceramic window, making it indispensable for firmware development, qualification testing, and field updates - whereas the alternatives trade programmability for cost or manufacturability.

Availability

DS87C520-WCL is available at Aetrix Electronics and suitable for industrial automation controllers, medical device bootloaders, legacy system upgrades, and EMI-sensitive instrumentation requiring stable component supply and long-term traceability.

Supply support for DS87C520-WCL 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 precision analog, mixed-signal, and high-reliability semiconductor solutions for industrial, medical, and communications markets.

The DS87C520-WCL belongs to Maxim's high-speed 8051-compatible microcontroller family, engineered to accelerate legacy 8051-based systems while preserving software and hardware compatibility - targeting cost-sensitive, performance-limited embedded applications needing field-upgradable firmware.

FAQ

What is the maximum operating frequency of the DS87C520-WCL?

The DS87C520-WCL supports a maximum crystal frequency of 33MHz, enabling an apparent execution speed of 82.5MHz (2.5× standard 8051) and single-cycle instructions completing in 121ns. This rating applies across its specified 0°C to +70°C temperature range and requires stable ±0.5% crystal tolerance and proper load capacitance per the datasheet layout guidelines.

How does the ROMSIZE feature work in the DS87C520-WCL?

The DS87C520-WCL uses the ROMSIZE register (SFR C2h, bits RMS2–RMS0) to dynamically configure the upper boundary of internal EPROM address decoding - selectable from 0kB to 16kB in powers of two. This allows the DS87C520-WCL to map external Flash into the 0000h–3FFFh space while keeping boot code in internal EPROM, enabling secure, field-upgradable firmware architectures without hardware changes.

Can the DS87C520-WCL be used as a drop-in replacement for standard 8051 microcontrollers?

Yes, the DS87C520-WCL is pin-compatible and instruction-set-compatible with standard 8051 devices in 40-pin DIP packages. Its default timer configuration runs at 12 clocks per increment to preserve legacy timing, and all I/O ports behave identically. However, DS87C520-WCL executes instructions 2.5× faster - so timing-critical software loops and baud rate generators may require recalibration unless using the built-in timer scaling.

What is the purpose of the windowed CERDIP package in the DS87C520-WCL?

The windowed ceramic DIP package in the DS87C520-WCL enables UV light erasure of its on-chip EPROM, allowing full firmware reprogramming after soldering. This makes the DS87C520-WCL ideal for development, prototyping, and low-volume field updates - unlike plastic DIP or mask ROM variants which lack erasability. The window must remain uncovered during UV exposure and protected from ambient light during normal operation.

Does the DS87C520-WCL support both internal and external data memory access simultaneously?

Yes, the DS87C520-WCL supports concurrent internal and external data memory access via the DME1/DME0 bits in PMR (C4h). When enabled, MOVX instructions to addresses 0000h–03FFh target the 1kB on-chip SRAM, while addresses above 03FFh route to external memory through Ports 0 and 2 - allowing hybrid memory architectures with zero wait-state internal storage and flexible external expansion.