6502.org

Hi,

I recently bought an eBay WDC65C02 chip which turned out to be a blacktop 65C02 but it was still fun. My first setup was on a breadboard with hardwired NOPs and it worked! I moved on to using a CPLD to drive the 65C02 and provide a real program. This worked as well!! Inspired by this success I purchased a WDC65C816, a WDC65C22 and SRAM from Mouser and lots of jumper wires on a triple wide breadboard. Blinky lights!

This whole thing has now morphed into using a BlackIce II FPGA board as the ROM/clock for the 65C816, the 65C22, 128KB SRAM (AS6C1008) on a hand-wired protoboard hat. I am thinking of adding a 32KB EEPROM and have purchased an AT28BV256. Is this a good option?

The EEPROM runs at 3.3V and can be programmed in-situ. It looks like it takes about 10s to program 64K. I plan to have the FPGA hold a bootrom which will allow the EEPROM to be programmed.

Anyway, this has been great fun so far and kudos to this site and the amazing amount of info and discussion.

Cheers,
Derek

Welcome - sounds like great progress! Good to see the blackice making itself useful in there.

I know there's experience with EEPROMs over on stardot: one thing to watch out for is to ensure there are no stray writes, because even if the chip is soft-locked to keep the data safe, it will still go into a write-handling mode which will disrupt subsequent reads for a while. (I see there are matches over there for AT28C256 but not AT28BV256)

Thanks for the welcome and the link. Lots of info and even some code there. It did resolve one concern I had because the manual for the AT28BV256 talks about 12V being required for chip erase but no mention of what is needed for writing. The threads on stardot don't mention 12V at all so I am led to believe that 12V is not needed for my usage.

I will watch out for the stray writes leading to disruption.

I programmed up EHBASIC into the FPGA BRAM on the BlackIce and I can now PEEK and POKE the EEPROM from BASIC. Here are some photos of my new toy. Even with all the knitting on the back it seems to work fine at 10MHz. The SRAM is 55ns so guess I shouldn't expect more. Maybe I will try it using the 10ns SRAM on the BlackIce. The EEPROM is much slower (200ns) so when I have programs in there it will be the limiting factor.