512k keyboard killed by a cable

[Gorgonops]

I think my issue wa mostly that schematic with the word "Intel" stamped loudly on the chip in question. Anyway... sure, if the "bottom pinout" of that Philips 8021 variant with the "socket top" is indeed the same as the mask part that was originally used and is 100% software code compatible that looks like the perfect replacement if one can be found. But, still, it's inaccurate to say in that one's case it "only takes a few wires" to use an external EPROM with it: that part quite literally has a fully decoded ROM socket glued on top with its own dedicated fully decoded bus already running to it. The PLCC version that's functionally identical has way more than 28 pins, with the extra dedicated to that same memory bus.

 

[BEU]

Thank You all for information about this complicated problem.  

Before I knew how complicated this problem is, I bought two MAB8021  cheap on ebay. Unclear whats in this MASK ROM.



I have not tried them.

Minimal circuit for a 8035:

http://www.theresistornetwork.com/2013/07/programming-vintage-intel-mcs-48.html?m=1

Probably this could work but looks rather complicated.

I was actually thinking of the MAB8401B as a sub-in for the MAB8021:

http://www.datasheetarchive.com/dl/Scans-005/Scans-00116775.pdf

You can actually just piggyback the EPROM right onto it. Or you can use the bond-out version MAB8401WP.

[SIZE=10pt]The MAB 8401B could be a solution but the You have to find the 8401B and an appropriate EPROM and program. Don’t know if the MAB8401B has the same pin designation as MAB 8021.[/SIZE]

[SIZE=10pt]The MAB 8401WP is 68 pin PLCC.    [/SIZE]

[SIZE=10pt]If I find a MAB8401B I will try it . Another way to solv this problem is to find another KB with working MAB8201.[/SIZE]

[SIZE=10pt]I will report later.[/SIZE]

[SIZE=10pt]          [/SIZE][SIZE=8pt]                       [/SIZE][SIZE=12.5pt]     [/SIZE]

 

[Paralel]

Mask ROM is the ROM program inside these little "microcomputers" that tells them how to function. Mask ROM means it was printer using photomasks in a process called photolithography. Mask ROM is like EPROM, except it isn't programmed electronically the program is actually etched into the face of the ROM using the lithographic process. Those 8021's you have, if they didn't come from a donor Mac keyboard, are useless, because you can't program the Mask ROM's yourself.

 

[BEU]

I realize that now.

Cant find any information about the chip from the label .

 

[mahmoud]

Apparently, for the MAB8021, if you apply 15V to the RESET pin, 15V to the PROG pin, and a TTL signal to the T1 pin, it will dump the internal Mask ROM to the Port 0 pin

Hi,

Paralel, Thank you for suggesting that method. Did you ever tried it out ever?

Actually I am willing to dump an INTEL's 8021 internal ROM. Does the above mentioned method works on INTEL's MCUs? 

 

[Grant]

Is there more technical information about keyboards using the 8021 or MAB8021? I've previously made a drop-in board for an 8021 that uses a newer smaller flash microcontroller. The code needs to be rewritten but if there is protocol information then I don't think it would be that hard. Also the physical space around the 8021 is a concern so I'd like to see photos of the keyboard guts. If I wanted to buy one or more of these keyboard models, the ones with the 8021 in it, what keyboards am I looking at?

So just to be clear, I'm talking about making a new 8021. This being a small board with the same footprint and approximate size of the keyboard controller IC.

 

[Dog Cow]

Is there more technical information about keyboards using the 8021 or MAB8021?

Try this: Engineering Specification for Macintosh Keyboard

 

[Grant]

Thanks. Aside from the schematic that looks pretty good.  I've done PS/2 protocol before and this looks somewhat similar (clock and one bidirectional data line).

 

[Joopmac]

Sorry to dig up this old topic

I have exactly the same issue, presumably by the same cause, wrong cable by previous owner

Any news on this 341-0222B copy or clone?