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GW-6830-1, a replacement for Motorola 6830 mask ROMs

glitch

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Finally got a prototype for the Motorola 6830 replacement done:



The above image shows the prototype lashed up to a Glitchbus 32K RAM board for testing. Closeup:



The MC6830 is a mask ROM which was used in a number of Motorola 6800 systems, such as the MEK6800D1 and D2 trainers/dev boards, SWTPC 6800, etc. Not only is it mask programmable, but the chip select polarities are also mask programmable. That means that a universal replacement must have selectable polarity too, which we've done using surface mount 0R jumper resistors. Since we ended up using an 8K EEPROM, there's an optional rotary switch included, which allows selecting the ROM image you want to be active. Handy for e.g. having MIKBUG and JBUG both available on your MEK6800D2, having a ROM-resident memory test for your SWTPC 6800, or just making custom ROM images available with stock images!

Here are some closups of just the module:





The flywires will be replaced with a pogo pin test fixture, which we haven't designed yet. The rotary switch used in the prototype is a through-hole version, since the J-lead surface mount version is currently on a long backorder. It's an expensive part -- around $8 in QTY 1 -- so it's optional for the GW-6830-1 if you only want a single ROM image.
 

deramp5113

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Great looking job! I literally started to make something like this a few months ago to make SWTBUG like I want it for my 6800. I ended up going with an external EPROM instead and putting a switch on the CPU board to swap between the original SWTBUG and the new one. Keep us posted!

Mike
 

glitch

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Thanks, will do! I'm going to try and get the pogo pin fixture done this week and off to the board house. Funny how we end up working on a lot of the same stuff so often :p
 

deramp5113

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What’s your plan for programming the part? Or more specifically, making it easy for an end user to write to the part? I considered making an adapter to give it a standard 27xx pinout, or a small SS-50 board with a socket for the part so I could write to it, but neither of those ideas is a cost effective solution.

Mike
 

glitch

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What’s your plan for programming the part? Or more specifically, making it easy for an end user to write to the part? I considered making an adapter to give it a standard 27xx pinout, or a small SS-50 board with a socket for the part so I could write to it, but neither of those ideas is a cost effective solution.

Mike

I'm going to do up a (probably PIC based) programmer so I can do volume-ish programming in shop, but I'll probably also just do a pogo pins adapter to a 28C64B type pinout. The problem is, there's sixteen possible configurations for the chip selects, so a programmer kinda needs to be able to either be told what they are (nixes the idea of just a simple adapter), figure it out on its own (what my programmer will do), or have some switches to manually set it up.

Also planning on a MEK6800D2-attached programmer, since that is after all one of the appnotes from Motorola :)
 
Joined
Jul 9, 2017
Messages
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Location
Sunnyvale, CA
Hi, Any update on the 6830 replacement adapter? I’ve started several restoration projects where they would be super helpful.
Happy to be a beta tester, definitely interested in acquiring several of them.

Stan
 
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