Analog Devices Inc./Maxim Integrated DS87C520-QCL+T&R

Overview

DS87C520-QCL+T&R from Maxim Integrated (now Analog Devices) is a high-speed, 8051-compatible microcontroller with 16kB on-chip EPROM, 1kB MOVX-accessible SRAM, and 256 bytes of scratchpad RAM. It executes instructions in 4 clocks/machine cycle (vs. 12 in standard 8051), achieving 33MHz max clock rate and 121ns single-cycle instruction time. It serves as a drop-in performance upgrade for legacy 8051-based industrial control, instrumentation, and embedded communication systems.

For engineers reviewing the DS87C520-QCL+T&R datasheet, DS87C520-QCL+T&R pinout, DS87C520-QCL+T&R application, or DS87C520-QCL+T&R equivalent, key selection considerations include its dual hardware serial ports, ROMSIZE register for dynamic external memory mapping, Power Management Mode for low-power operation, and PLCC-44 package compatibility with existing 8051 sockets.

Technical Context

The DS87C520-QCL+T&R implements a redesigned 8051 core eliminating dummy memory cycles, delivering 2.5× average speed improvement over standard 8051 at identical crystal frequency. Its architecture supports four-clock-per-machine-cycle execution while maintaining full 8051 instruction set and SFR compatibility - including extended registers like DPS (Dual Data Pointer Select) and PMR (Power Management Register).

It integrates two full-duplex UARTs, three 16-bit timer/counters (with optional 4-clock timing), programmable watchdog timer, power-fail reset, and early-warning interrupt. Memory access is enhanced via dual DPTRs and configurable MOVX stretch (2–9 machine cycles), enabling seamless interfacing with both fast SRAM and slow peripherals without glue logic.

Key Specifications

Pinout & Package

DS87C520-QCL+T&R is supplied in a 44-pin Plastic Leaded Chip Carrier (PLCC) package with J-lead configuration, RoHS-compliant and lead(Pb)-free. Pinout matches standard 8051 family layout for drop-in replacement in PLCC-44 sockets.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8051-compatible microcontroller applications.

Compared with DS87C520-QCL+T&R, DS83C520-QCL+T&R offers identical performance and packaging but eliminates field-programmability for cost reduction, while AT89C51ED2-RLTUM trades dual UARTs and ROMSIZE flexibility for integrated USB - making it unsuitable for legacy 8051 drop-in upgrades requiring those features.

Availability

DS87C520-QCL+T&R is available at Aetrix Electronics and suitable for industrial automation, smart metering, and medical diagnostics requiring stable component supply, long-term lifecycle support, and RoHS-compliant PLCC packaging.

Supply support for DS87C520-QCL+T&R 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 (acquired by Analog Devices in 2021) is a leader in precision analog, mixed-signal, and high-reliability semiconductor solutions for industrial, automotive, and communications markets.

The DS87C520-QCL+T&R belongs to Maxim's high-speed 8051 microcontroller family, designed specifically to extend the life of legacy 8051-based systems through performance uplift, enhanced memory management, and robust power/failure handling - without requiring architectural overhaul.

FAQ

What is the maximum operating frequency of the DS87C520-QCL+T&R?

The DS87C520-QCL+T&R supports a maximum crystal frequency of 33MHz, enabling a machine cycle rate of 8.25MHz (33MHz ÷ 4). At this speed, the fastest instruction executes in 121ns. This specification is guaranteed across the commercial temperature range (0°C to +70°C) and applies directly to the DS87C520-QCL+T&R in its 44-pin PLCC package.

Does the DS87C520-QCL+T&R support in-system programming (ISP)?

No, the DS87C520-QCL+T&R does not support in-system programming. It contains factory-programmed EPROM that requires UV erasure (via windowed CERDIP variants) or is one-time programmable (OTP) in plastic packages. The DS87C520-QCL+T&R uses OTP EPROM - once programmed, code cannot be rewritten electrically or in-circuit.

How does the ROMSIZE feature work in the DS87C520-QCL+T&R?

The ROMSIZE register (SFR C2h) in the DS87C520-QCL+T&R lets software dynamically configure the upper boundary of on-chip program memory - from 0kB to 16kB in steps (e.g., 4kB at 0FFFh). This enables external flash to occupy addresses normally reserved for internal ROM, supporting secure boot and firmware updates. The DS87C520-QCL+T&R defaults to 16kB after reset.

Can the DS87C520-QCL+T&R replace a standard 8051 in a PLCC-44 socket?

Yes, the DS87C520-QCL+T&R is pin-compatible with standard 8051 microcontrollers in the 44-pin PLCC package. Its pinout matches industry-standard 8051 layouts, including identical placement of VCC, GND, RST, XTAL1/2, P0–P3, and control signals. Firmware typically runs unchanged, though timing-critical code may require adjustment due to the 4-clock-per-cycle speedup.

What is the function of the dual data pointers in the DS87C520-QCL+T&R?

The DS87C520-QCL+T&R provides two independent 16-bit data pointers (DPTR0 at 82h/83h and DPTR1 at 84h/85h), selected via the DPS bit (PMR.7). This eliminates repeated DPTR reloads during block memory transfers - for example, moving data from external RAM to internal SRAM - reducing instruction count and execution time by up to 50% compared to single-DPTR 8051 implementations.