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

Overview

DS87C520-QCL/T&R from Maxim Integrated is an 8051-compatible high-speed microcontroller in 44-pin PLCC 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-block flexibility in embedded control 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 44-pin PLCC footprint, 33MHz max clock, dual serial port support, ROMSIZE register programmability, and Power Management Mode for low-power operation in portable instrumentation and industrial controllers.

Technical Context

The DS87C520-QCL/T&R implements a redesigned 8051 core eliminating dummy memory cycles, achieving 2.5× average speedup over standard 8051 at same 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 instruction set compatibility.

It integrates two independent 16-bit timer/counters (T0/T1 default to 12-clock mode for backward compatibility; T2 supports capture/reload), seven external interrupts (INT2–INT5 on Port 1), programmable watchdog timer, power-fail reset, and early-warning power-fail interrupt. Memory access is configurable via ROMSIZE (C2h) and DME bits (PMR.1/.0) to enable/disable 1kB on-chip SRAM at 0000h–03FFh.

Key Specifications

Pinout & Package

DS87C520-QCL/T&R is housed in a 44-pin Plastic Leaded Chip Carrier (PLCC) package with J-lead geometry, rated for 0°C to +70°C operation and RoHS-compliant (QCL+ variant). Pin 1 is located at the index corner adjacent to the notch.

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 offers lower unit cost for fixed firmware but sacrifices field-programmability, while AT89C51RD2-RLTUM provides Flash flexibility at the expense of 2.5× slower execution and missing power-fail and EMI-reduction features critical for industrial reliability.

Availability

DS87C520-QCL/T&R is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, automotive body control modules, and smart energy meters requiring stable component supply across extended product lifecycles.

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 (now part of Analog Devices) designs precision analog, mixed-signal, and high-reliability microcontrollers for demanding industrial, medical, and automotive applications.

The DS87C520-QCL/T&R belongs to Maxim's high-speed 8051-compatible microcontroller family, engineered to deliver deterministic real-time performance, robust power management, and enhanced peripheral integration for resource-constrained embedded control systems.

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 peak instruction cycle rate of 8.25 MIPS with single-cycle execution in 121ns. This is achieved through its 4-clock-per-machine-cycle architecture, which delivers approximately 2.5× faster average performance than standard 8051 devices running at the same crystal speed. The DS87C520-QCL/T&R maintains full 8051 instruction set compatibility while achieving this speed increase via architectural optimization rather than simple clock scaling.

Does the DS87C520-QCL/T&R support in-system programming of its on-chip EPROM?

No, the DS87C520-QCL/T&R does not support in-system programming. Its 16kB on-chip memory is EPROM (erasable programmable read-only memory), requiring UV erasure through the quartz window in the CERDIP variant. The DS87C520-QCL/T&R uses a 44-pin PLCC package without a window, meaning its EPROM content is programmed once during manufacturing and cannot be electrically erased or reprogrammed in-circuit. For field-upgradable alternatives, consider Flash-based derivatives like the DS89C450, though they lack the DS87C520-QCL/T&R's specific ROMSIZE and dual-serial features.

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

The ROMSIZE feature in the DS87C520-QCL/T&R is controlled by bits RMS2–RMS0 in SFR address C2h and dynamically selects the upper boundary of on-chip program memory decoding - from 0kB to 16kB in powers of two. When configured for less than 16kB (e.g., 4kB at 0FFFh), addresses above that boundary automatically route to external program memory via P0/P2, enabling external flash to serve as a boot block. This allows the DS87C520-QCL/T&R to execute startup code from external memory while retaining internal EPROM for application code, all without hardware changes. The reset default is 16kB.

Can the DS87C520-QCL/T&R operate in low-power modes, and how is this implemented?

Yes, the DS87C520-QCL/T&R implements Power Management Mode (PMM) via the PMR register (C4h), allowing software to select a reduced CPU clock rate of either crystal/64 or crystal/1024. In PMM, the machine cycle rate drops from 4 clocks per cycle to 64 or 1024 clocks per cycle, reducing dynamic power consumption proportionally - e.g., at 12MHz crystal, PMM yields 187.5kHz or 11.7kHz machine cycle rates. Exit from PMM is automatic on any interrupt or reset, ensuring deterministic wake-up latency. This makes the DS87C520-QCL/T&R suitable for battery-powered applications requiring extended standby duration.

What are the key differences between DS87C520-QCL/T&R and DS83C520-QCL?

The DS87C520-QCL/T&R and DS83C520-QCL share identical pinout, timing, SFR map, and peripheral functionality, but differ in program memory technology: DS87C520-QCL/T&R uses EPROM (UV-erasable, one-time programmable in PLCC), while DS83C520-QCL uses factory mask ROM (fixed firmware, lower unit cost for high volumes). All references to DS87C520-QCL/T&R features apply to DS83C520-QCL except EPROM-specific operations. Neither device supports in-system programming; both require external programmers for initial programming (DS87C520-QCL/T&R) or mask generation (DS83C520-QCL).