Scott, I recommend before you jump into a REX solution that you read my REX# and REXCPM wiki pages at Bitchin100. REX Classic is the DIY option, but I no longer support it, and it has known defects. My 2 cents as the designer... Steve
On Sat, Dec 19, 2020 at 6:12 PM Brian White <b.kenyo...@gmail.com> wrote: > Actually with rex classic you don't even need any rom in the main rom > socket so you don't need any of those boards, just a single wire from the > /CS pin in the main rom socket out to the REX. You just can't run the > machine *without* the rex after that without opening back up to put a rom > back. The flexrom board just lets you install or remove the rex at will, as > well as being re-writable itself by being a 28C256. > > On Sat, Dec 19, 2020, 6:04 PM Brian White <b.kenyo...@gmail.com> wrote: > >> >> >> On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell <mcdonnell.j...@comcast.net> >> wrote: >> >>> Now that I have proven out that a 27C256 EPROM is working fine in this >>> one, I am going to play around with customizing it. The real ULTIMATE would >>> be to replace the ROM with an EEPROM (like 28C256) and add in some type of >>> loader where you could update the main firmware over serial. That may not >>> be possible because often in these 80’s computers they usually placed some >>> IO address space in the ROM area (since write is not possible to the ROM) >>> and decoded it using the write signal and address. It was a simple trick >>> for accessing output only IO. I am talking out of my rear end right now >>> because I haven’t studied the schematic/memory map in detail yet. >>> >> >> http://tandy.wiki/FlexROM_100 >> >> http://tandy.wiki/FlexROM_102 >> >> Especially in concert with REX Classic >> >> http://tandy.wiki/Building_a_REX >> or >> arcadeshopper.com sometimes has rex classic pre-built you can just buy. >> >> You'd use the FlexROM_102 in the 100 that has the standard pinout. >> >> If you don't care about using the fully software loadable main rom via >> REX, and only need a plain 28C256 to 27C256 adapter without the /CS >> breakout remote loop, this would be a bit more convenient because it >> doesn't need a soic-28 test clip to program it. >> >> http://tandy.wiki/28C256_to_27C256 >> >> You just switch a couple jumpers and pop the board right in the >> programmer. >> >>>
