That would make sense if these were OTP or fused parts.
Wouter, can you check the pins with an ohm meter, to what we think are power
and ground. Outputs usually look different than inputs.
Dwight
________________________________
From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Brent Hilpert via
cctalk <cctalk@classiccmp.org>
Sent: Thursday, October 10, 2019 10:22 AM
To: General Discussion: On-Topic Posts <cct...@classiccmp.org>
Subject: Re: Mystery chip SCM44506L
On 2019-Oct-10, at 5:33 AM, Wouter de Waal via cctech wrote:
>> Very likely a semi custom or custom memory device, due to the prefix.
>
> Armed with that and the fact that pin 1 connects to the leadframe I figured
> maybe it's something like the 6830 Mikbug prom -- 0V on 1, 5V on 12, data on
> the left, address on the right. Tried reading it like that (for all 16
> combinations of chip selects) but 0xFF throughout.
>
> So I popped the lid, stuck it under a microscope. The chip says "MCM6816"
> which is in fact a 1k ROM.
>
> Anyone have more information on the 6816 ROM?
Funny, the usual goto reference for early 6800-series chips is the 6800 Micro
System Design manual:
http://bitsavers.org/components/motorola/6800/MC6800_Microcomputer_System_Design_Data_1976.pdf
but it's not in there.
There are a couple of other 1K ROMs however (6830,68308).
Might compare pinout with those.
