Blob-top memory unknown pinout

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krzysiobal
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Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland

Blob-top memory unknown pinout

Post by krzysiobal » Thu Sep 14, 2017 1:17 pm

I am reverse engineering ASDER 20 in 1 multicart.
While the 4 Mbit PRG memory has pinout the same like 27c040, 2Mbit CHR has quite weird pinout. Do you know name of any eprom chip with same pinout?

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lidnariq
Posts: 9401
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Blob-top memory unknown pinout

Post by lidnariq » Thu Sep 14, 2017 2:08 pm

It's not too different from the 40-pin 16-bit data bus UVEPROMs. (e.g. look at 27C4100 and 27C4096) By which I mean "address bus mostly in order" and "data bus in order if you skip the high byte".

But I don't know of an exact match.

lidnariq
Posts: 9401
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Blob-top memory unknown pinout

Post by lidnariq » Sat Sep 16, 2017 10:32 am

I was digging around some more and found this random pinout reference of a bunch of ROMs used on a bunch of random arcade boards. Most of them are similar to the JEDEC standard pinout, but this is conspicuously different:

Code: Select all

(4M) 512k x 8 mask rom
       HN62304

A8   1 +-v-+ 32  A9
A7   2 |   | 31  A10
A6   3 |   | 30  A11
A5   4 |   | 29  A12
A4   5 |   | 28  A13
A3   6 |   | 27  A14
A2   7 |   | 26  A15
A1   8 |   | 25  A16
oe?  9 |   | 24  A17
gnd 10 |   | 23  A18
ce? 11 |   | 22  gnd
D0  12 |   | 21  A0
D1  13 |   | 20  D7
D2  14 |   | 19  D6
D3  15 |   | 18  D5
+5v 16 +---+ 17  D4
I find it amusing that this is clearly a 16-bit ROM where they've just chosen to not wire bond D8-D14, and wire bonded /BYTE to ground internally.

NewRisingSun
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Joined: Thu May 19, 2005 11:30 am

Re: Blob-top memory unknown pinout

Post by NewRisingSun » Sat Nov 04, 2017 2:24 pm

krzysiobal: Could you please check whether game number 14 (Benico) has graphical errors during the attract mode that plays after waiting at that individual game's title screen for a few seconds?

krzysiobal
Posts: 718
Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland

Re: Blob-top memory unknown pinout

Post by krzysiobal » Sat Nov 04, 2017 5:05 pm

Yes, it has.
Here is my fix:
Attachments
ASDER 20-in-1 (Unl)[U][!] [Benico fix].ips
(40 Bytes) Downloaded 186 times

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