Analog Devices Inc./Maxim Integrated DS87C530-QCL

Overview

DS87C530-QCL from Maxim Integrated (formerly Dallas Semiconductor) is a high-speed, 8051-compatible EPROM microcontroller with integrated real-time clock (RTC), battery-backed 1kB SRAM, and dual serial ports. It operates at up to 33 MHz with 4-clock-per-machine-cycle architecture, delivers single-cycle instructions in 121 ns, and supports dynamic ROMSIZE selection for flexible external memory mapping - used in portable instrumentation and data-logging systems requiring time-stamped nonvolatile storage.

For engineers reviewing the DS87C530-QCL datasheet, DS87C530-QCL pinout, DS87C530-QCL application, or DS87C530-QCL equivalent, key selection considerations include its 52-pin PLCC package, RTCX1/RTCX2 crystal interface, VBAT-backed SRAM retention, ROMSIZE register configurability, and compatibility with legacy 8051 firmware while delivering ~2.5× average speed improvement.

Technical Context

The DS87C530-QCL implements a static CMOS 8051-compatible core with 4-clock-per-instruction-cycle execution, eliminating dummy memory cycles present in standard 8051s. Its instruction timing differs from legacy 8051s, though all opcodes retain identical functional behavior and flag effects.

It integrates dedicated RTC circuitry with alarm interrupt, independent VCC2/GND2 power domain for noise isolation, and hardware power-fail detection with early-warning interrupt. The ROMSIZE register (C2h) enables software-selectable on-chip ROM address limits (0–16 kB), allowing seamless boot-from-external-Flash configurations without hardware changes.

Key Specifications

Pinout & Package

DS87C530-QCL is housed in a 52-pin Plastic Leaded Chip Carrier (PLCC) with J-lead configuration. Pin numbering follows standard PLCC top-view orientation (pin 1 marked by corner notch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS83C530-QCL, DS87C530-QCL offers field-programmable EPROM for development agility; compared with MAX32660GWE+T, it provides drop-in 8051 firmware compatibility and 5 V robustness at lower clock speeds - making DS87C530-QCL optimal for maintaining or upgrading legacy instrumentation platforms.

Availability

DS87C530-QCL is available at Aetrix Electronics and suitable for portable instrumentation, industrial HMI panels, medical handhelds, and smart metering applications requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.

Supply support for DS87C530-QCL 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 embedded processing solutions for industrial, medical, and communications markets.

The DS87C530-QCL belongs to Maxim's high-speed 8051 microcontroller family, engineered to extend legacy 8051 ecosystems with integrated RTC, nonvolatile SRAM, and power-efficient operation for battery-backed embedded instrumentation.

FAQ

What is the maximum operating frequency of the DS87C530-QCL?

The DS87C530-QCL supports a maximum clock frequency of 33 MHz, enabling single-cycle instruction execution in 121 ns. This is achieved through its 4-clock-per-machine-cycle architecture - a 3× speed improvement over standard 8051 cores running at the same crystal frequency. The DS87C530-QCL maintains full 8051 instruction-set compatibility while delivering this performance gain.

Does the DS87C530-QCL require an external crystal for the real-time clock?

Yes, the DS87C530-QCL requires an external 32.768 kHz crystal connected between RTCX1 and RTCX2 pins to operate the integrated real-time clock. The device supports both 6 pF and 12.5 pF load capacitance crystals, selected via the TRIM register (bit 6). A guard ring tied to GND2 is recommended around these pins to minimize noise coupling into the RTC oscillator circuit.

How does the ROMSIZE feature work in the DS87C530-QCL?

The DS87C530-QCL uses the ROMSIZE register (address C2h) to dynamically configure the upper limit of on-chip EPROM address space - selectable from 0 kB to 16 kB in powers of two. This allows software to temporarily "hide" internal ROM and access external memory (e.g., Flash) at overlapping addresses, enabling boot-from-external-memory configurations while retaining internal firmware for recovery. The EA pin overrides this setting when pulled low.

Can the DS87C530-QCL retain data in SRAM during main power loss?

Yes, the DS87C530-QCL retains data in its 1 kB on-chip SRAM during main power loss when a backup energy source (e.g., 3 V lithium battery or supercapacitor) is connected to the VBAT pin. Internal switching circuitry automatically transfers SRAM power from VCC to VBAT when VCC drops below VBAT. The 256 B scratchpad RAM remains volatile and is not backed up.

Is the DS87C530-QCL pin-compatible with standard 8051 microcontrollers?

No, the DS87C530-QCL is not pin-compatible with standard 8051 microcontrollers due to added pins for RTC (RTCX1, RTCX2), isolated RTC power (VCC2, GND2), and battery backup (VBAT). While it retains the same 52-pin PLCC footprint as some 8051 variants, the pin assignments differ - particularly for Port 0/2 multiplexing and dedicated RTC functions. Firmware is compatible, but hardware layout requires redesign.