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. > >>
