Old MOS Mask-Programmed ROM forgetfulness?
jrr at flippers.com
Tue Feb 16 02:04:33 CST 2016
On 02/15/2016 11:25 PM, Eric Smith wrote:
> On Mon, Feb 15, 2016 at 11:31 PM, John Robertson <jrr at flippers.com> wrote:
>> Rick, if you want to archive these PROMs (highly recommended) you should be
>> able to find a Data I/O 29B and get one of the programming packs that
>> supports NS chips. I may have such a combination in my collection, but that
>> PROM is not listed in my DATA I/O library of readable parts.
> They're not PROMs, they are masked ROMs, and there is *NO* equivalent
> PROM, so it's unlikely that there's any support for reading them on
> any PROM programmer.
>> Part of the
>> problem with the early PROMs is they needed a Sync or Clock signal to be
>> able to be read.
> The MM4221/5221 is fully static, so it doesn't have that particular problem.
> It's PMOS, and needs +5V and -12V supplies. The outputs are
> TTL-compatible, but the inputs technically are not, due to Vih min of
> 3.0V. Could be driven by TTL with a pullup resistor, or by CMOS.
Does it share the same pinout as the 1702 MOS Eprom? I can read and
program those EPROMs in my shop. The 1705 has a Vcc of +5, and a Vdd of
-9 to a maximum of -20VDC, it is a 24 pin device though.
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