Motorola MCM6570, 8192-Bit Custom ROM for Character Generator

[sfeinsmi]

I have a Technical Designs Labs Video Display Board (VDB) with a customized ROM Character Generator. The chip is labeled as follows:

VDB-2
7739 A
SCM37726P

The chip showed as a Motorola symbol.

It was clear it came from the MCM6570 series. I plan to pull out and try to dump the codes from the masked ROM because it was the only chip I have, and it is a rare item nowadays. There was no replacement available. I searched the Internet to find if someone may be solved for a substitute such as E2PROM or a similar one. The alternative was MCM6670 as a single +5V to run the character generator. Unfortunately, it was obsolete and no longer available for replacement nowadays.

I often wonder if modern chips such as FPGA can be created as much as MCM6570 feature such as four-row selects (RS0 to RS4). Perhaps you may know to resolve this kind of challenging situation.

Thank you,
Steven

 

[Al Kossow]

https://www.ebay.com/itm/255226708829 ?

 

[Chuck(G)]

I remember, many years ago, looking at the data book with the 6571 and thinking "what a clever way to avoid adding more ROM". Of course, this chip dates from the early 1970s when ROMs were smaller. Nowadays you could use a commodity PROM to do the character generation in a full 16x8 matrix without any of the fancy shift logic. That would be a 16Kbit PROM.

 

[Eudimorphodon]

Nowadays you could use a commodity PROM to do the character generation in a full 16x8 matrix without any of the fancy shift logic. That would be a 16Kbit PROM.

Yeah, I’m not sure what the point would be of trying to recreate the internal matrix shifting of the original chip in an FPGA or whatever when a plain old EPROM could be programmed to output the same results. How the MCM ”faked” a larger matrix than it could actually fill internally isn’t externally visible in the output.