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Hitachi 4864P-2 Memory Tester

This is a Arduino sketch to test Hitachi HM4864P-2 dynamic memory chips, used in some Commodore C64 boards. It was written using plain avr-libc omitting the Arduino bootloader, mainly due to poor switching speed of Arduino's digitalWrite() (overhead up to 40 times slower) and 10us upper limit for HM4864P-2 RAS strobe.

Prerequisites

All you need are:

  • Arduino Uno or any pin compatible board.
  • ISP programmer (I use stk500 compatible programmer).
  • A single HM4864P-2 chip.
  • Optionally, a single LED if the built-in LED on pin 13 (PB5) is not visible enough.
  • avr-gcc
  • avr-libc
  • AVRDUDE

Installation

Upon successful build of the circuit as shown below, attach (via the ICSP connector) and set the proper ISP programmer device in Makefile, and then just type in:

make flash

This will build the firmware and flash it to the connected device.

Operation

  • LED is glowing continuously - memory chip has passed all tests.
  • LED is blinking - memory chip is damaged.

Schematics

Schematics

Disclaimer

  • This is a simple educational project, and was developed to this sole purpose.
  • Nevertheless, you should be able to diagnose failed memory chips in your Commodore C64 board.
  • I take no responsibility for any negative outcomes or damage you may cause using this project.