VT101 8085 CPU Fault

Matt Burke matt at 9track.net
Tue Jan 20 17:19:46 CST 2015

On 20/01/2015 05:06, Robert Jarratt wrote:
> Do you recall what EPROM you used and how its pinout differed from the ROM
> you were replacing? As far as I can tell there is only one ROM on the board,
> could it be both the character ROM and the firmware?

I used a 2716, but you will probably need a 2764 for the ROM in
question. If you look at the four ROMs  on the VT100 schematic you will
see that the chip select pins are different for each one. Mask ROMs can
be manufactured with any combination of chip select required whereas
EPROMs are fixed. This means that the four mask ROMs can be installed in
any order.

There should be a separate ROM on the board for the character generator.
The part number will be something like 23-018E2-00. It's usually
soldered in.


More information about the cctalk mailing list