Intel 8755/8755A programming adapter added to HVEPROM project

The Intel 8755 is a chip I come across quite often inside vintage equipment, but, I’ve never stopped to look at what it does. That is, until recently when I was asked by a reader if I had anything to program one with.

The above sample is dated 1998? Apparently Intel was still cranking out 8755’s 22 years from first introduction!

The 8755 is an unusual offering, combining a 16kbit (2kbyte) EPROM and two 8-bit GPIO ports into a single package. Just the kind of thing you’d be wanting if designing a system based on an 8-bit microprocessor. The EPROM would be used to store a simple bootloader, and the GPIOs purposed for various system functions.

There are many other use-cases, for example on pluggable peripherals where more GPIOs are required, along with peripheral specific data or firmware.

From a technology standpoint, the 8755 appears to be the GPIO and EPROM portions of the 8749 MCS-48, minus the MCU core. This is evident from the matching headline specification, and that the programming algorithm, timings and voltages are the same as the MCS-48 family. This means that my MCS-48 programming shield would be able to program it with a simple adapter.

This is also how it was done in the day, with Intel documentation referring to MCS-48 programming hardware and adapters as a programming solution for the 8755.

Unfortunately because of differences in the programming interface, some software changes are required. Those who have already built the MCS-48 shield would need to get the latest host software and re-flash with the latest firmware to get 8755 support.

All build resources for this are on the MCS-48 shield page.

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