System 80 ROM

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System 80 ROM

Postby boxchester on Mon Aug 06, 2012 1:53 pm

I am wondering if anyone here is able to provide duplicates of the ROMs for the Video Genie I.

And also I have another question which needs an expert to answer, and I'm not very hopeful of anyone knowing the answer. The question is this: On the TRS-80 level I board, there are 2 ROMs each 2K 2716's, ROM A and ROM B for a total of 4K ROM. The schematic shows pin 18 on the ROMa chip (Chip select 0) which is tied to A11 to be an active LOW input pin. The same pin 18 on the ROMB chip, also tied to A11, is shown as an active HIGH input. Same pin, same chips, different function????? (A11 switching from 0 to 1 deselects ROMA and selects ROMB)
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Re: System 80 ROM

Postby tezza on Mon Aug 06, 2012 3:25 pm

I have burnt one of these ROMS in my time but it was a while ago. I'll have to dig the info out (or at least try to remember what I did). Which one do you need?

As to the answer to your second question, if I was you I would post it on the TRS-80 Yahoo Groups discussion board. One of the techies there will know the answer.
http://tech.groups.yahoo.com/group/TRS-80/
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Re: System 80 ROM

Postby tezza on Mon Aug 06, 2012 9:31 pm

Re: burning ROMS. Ok, now I remember. This is one of the few projects I didn't bother to document on the website.

Burning a ROM can be done. I have the ROM images if you want them. A 2732 can be used as a replacement. However, to use these in a System 80 they have to sit in an adapter (I make mine from two blank sockets) OR the socket needs to be re-wired. Essentially pins 18 and 21 need to be swapped. Problem with an adapter is that the chip might then sit too high and interfere with the keyboard placement. There is not much room in that space. You really have to try it. I'm assuming you would be able to wire it up or modify the socket yourself?

If you can't burn your own you could send me a couple of good 2732's I can burn one for you and return it, keeping the other one for my trouble?
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Re: System 80 ROM

Postby boxchester on Thu Aug 16, 2012 1:10 pm

Hi Tezza Sorry I didn't know you responded - I thought I would get an email if anyone responded to my post, and I haven't been back here until now. I am still investigating this circuit board, and will get back to you re your offer shortly.
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Re: System 80 ROM

Postby tezza on Thu Aug 16, 2012 2:53 pm

No worries Don,

Hmm..I thought anyone who posted in a thread got an email reply too, but maybe you have to specifically subscribed to the tread (see the subscribe link at the bottom). I subscribe to all forums so I automatically get all postings.
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Re: System 80 ROM

Postby boxchester on Sun Aug 19, 2012 3:59 pm

Thanks heaps for telling me about swapping pins 21 and 18! I would have gone ahead and just stuck them in without knowing. I will let you know shortly if I need the ROMs from you. Thanks a lot!
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Re: System 80 ROM

Postby tezza on Sun Aug 19, 2012 10:25 pm

Yes, that applies to the three main ROM sockets, if you want to use a 2732. The forth socket closest to the front (i.e. the ROM extension) takes a straight 2716 without pin swapping.
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Re: System 80 ROM

Postby boxchester on Mon Aug 20, 2012 1:31 pm

Hi Terry I am about to buy a lot of 10 new 2732 eproms (see http://www.ebay.com/itm/Lot-of-10-New-a ... 3f1b29932f) so if i send these to you for programming, could you program a set of 3 for me and keep the 7 unused ones? Rather than get them sent to me then on to you, could I send them straight to you? If ok , please send me your shipping address. I will also send some 2716's and if you could program 1 for me and keep the rest that would be very much appreciated.
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Re: System 80 ROM

Postby tezza on Mon Aug 20, 2012 3:42 pm

That's fine. I'll send you a PM with my address.
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