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Commodore PET BASIC 2

D

dansretropod

Member
Joined
Jul 2, 2012
Messages
34
Location
UK
Hi,

I'm trying to repair a 3032 PET which has BASIC 2. I know the ROMS/screen RAM and from what I can tell the Main RAM work and would like to disassemble the BASIC 2 ROMs to try and trouble shoot the problems.

My question is: Where does execution start when a 3032 BASIC 2 equipped PET is turned on, what address does execution commence at?

Also, if anyone knows of a BASIC 2 ROM disassembly then I'd love to see it.

Thanks!
 
If you think it'll help by all means work through the BASIC disassembly (I thought that Andre had only put the original and v4 up on 6502, guess I'll have to look again) but I kinda think you're looking in the wrong places for your problem.

Did you try filling the video RAM directly as I suggested in the other thread so you can rule out the video section?
 
Hi,

Thanks for your advice guys, I've gone through the ROM disassembly, adding code at certain points to verify the CPU is getting that far and by outputting certain info to the screen I was able to see the error of my ways, I am using the wrong EPROM type in E000-EFFF! (Screen Editor).

My PET had a bad Edit ROM so I thought I would just use a 2532 EPROM and put the rom file on that, little realising it needs to be a 2716 in that socket otherwise all the IO registers screw up! doh!

So I'm closer now to getting this computer working, I just need some blank 2716's which I can get on ebay I see. In the meantime, is it possible to adapt a 2532 to work in the edit rom socket? Disabling a pin or something?

Thanks for your help!
 
dansretropod said:
In the meantime, is it possible to adapt a 2532 to work in the edit rom socket? Disabling a pin or something?
Click to expand...

You can not easily use a 2532 in the 2K editor socket because the entire 4K chip is enabled in the 3032. You would have to add a NAND gate in the chip select path to enable it only during the first 2K address space. Oddly, if you happen to have a 2732, you can use a 2732 directly in that socket if you place the 2K editor data in the upper 2K of the 2732 space. Unique differences in the 2732 pinout VS the 2532 allow this to work.
 
Thank you very much Dave. I didn't realise there was such a difference between 2732 and 2532. As I don't have any 2732 or 2716's I will order a couple from Ebay.

It's strange that in the 3032 the entire 4K of the edit ROM is used. I've used 2532's before in a 4032 PET Screen editor ROM with no problems, but this one caught me out!

Thanks again
 
dansretropod said:
It's strange that in the 3032 the entire 4K of the edit ROM is used. I've used 2532's before in a 4032 PET Screen editor ROM with no problems, but this one caught me out!

Thanks again
Click to expand...

Yes, that seems to get us all the first time. This link below will show the schematic of the ROMs in the 4032/8032 machines. Notice the gates at the chip enable of the E000 socket. Both the SEL E_bar and the x8xxx have to be low (0 state) to select the E socket. So only address from E000-E777 are enabled. The 3032 does not have the gates.

http://zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ2/8032087-04.gif

Here is a link to the data sheet on the 2532 EPROM.

http://generalthomas.com/Old_Test_Equipment/TMS2532.pdf
 
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