In SX Microcontrollers, SX/B Compiler and SX-Key Tool, mebikerider wrote:

Thanks for all the kind words! 

In the project section, I've posted a project with a picture of my board, more recent code and a few documents.

The code listed above was an old development piece. For the project, I cleaned it up a bit and doublechecked that the RAM, the RS232 for the PC two-way communication and the RS232 for the LCD display all work properly.

James, the code attached to the project might be better for the SXLIST site, and you're welcome to post it.

I include a few references that helped - the SIMM socket pinout and a sample of code that shows the usage of each pin and gives examples of how to access the DRAM.

Chris, I also used the Z80 quite a bit in years past, and I remember its built-in refresh support. It supported a refresh mode where actual addresses were provided to the RAM, which led me to think that refresh would be a complicated procedure. But then I learned that modern SIMMs have a refresh mode where a counter internal to the DRAM chips manages all addressing, so all we need to do nowadays is toggle a couple of SIMM control lines on every ISR, and we're done.

This was a fun little project, especially because it worked so well, so quickly, even while using surplus parts.

David

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