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PET ROM/RAM replacement board

If you have RAM that can be modified as the program runs along, I can send you the DASM source of the little routine I had a shot at a while ago. While I can't say for sure it will behave as intended, emulator runs suggests it might.
 
Would be quite interested to take a look at the DASM routine if you get a chance..

Tonight I made some progress on my first foray into 6502 assembler..
Wrote a small program which copies the contents of a ROM into the PETvet's RAM. I was able to read out the contents of the c000-cfff ROM from my PET 2001 mainboard into the PETvet's RAM, then halt the CPU and read out the contents over a serial port. With some additional code on the microcontroller, it would be possible to compare the copied ROM image with a stored image in the MCU's flash, to test individual ROMs. This program is selectable as a setting with the PETvet's jumpers as a RAM/ROM test mode.

Next thing will be a memory tester. I'm thinking about how best to test the PET's RAM and detect which chips may be bad.. I'll look over the schematics to get some insights.
I'm also thinking it would be nice to have a second board to connect to the PETvet to turn it into a fully working 6502 computer in its own right. All you would need would be a clock, reset, and whatever I/O you wanted. Should be possible to use the the MCU as a serial terminal.
 
Any chance of getting a updated firmware with the correct roms for a 60hz 40 col universal board?

I've hooked up a disk drive to my 4016 with no display and can't get any disk commands to work blind, and I'm wondering if the keyboard is flakey or if the ieee port is bad, the 80col rom has video memory addressed differently, so I get nothing from the petvet when I view video memory.

Thanks!

Later,
dabone
 
Hey dabone,

Sure, I can get you the updated firmware -
Do you know the ROMs and addresses for the 60hz/40 col board? I will check on Zimmers.net to look.
 
Give this a try:

http://bitfixer.com/bf/data/petvetupdate.bin

You'll need to flash the firmware over a serial connection, described here:
http://www.bitfixer.com/bf/petvet/petvet-operation

To do the updates, I usually remove the PETvet from the PET main board, connect it to power (requires 5V, described in a moment), and follow the XMODEM transfer procedure described on the site. I'll post the pinout of the 6-pin ISP header in a moment, I usually use that to power the PETvet during updates.
You can also use the PET mainboard to provide power to the PETvet during the update, then you won't need to bother with the ISP connection.
 
I'm having trouble getting it to take the update, it acted like it did once, but the switch setting you give come back as basic2.

Duh, missed the part about changing the jumper to begin programming....

Switch 1 OFF
Switch 2 ON
Switch 3 ON
B4 40CRTC
PETvet ready.
Press any key to halt CPU and enter diagnostic mode.
Halting CPU..PETvet Diagnostic Mode
1. Display Memory Range
2. Display PET Screen Memory
3. Exit Diagnostic Mode
Enter selection: Display Screen Memory

*** COMMODORE BASIC 4.0 ***

31743 BYTES FREE

READY.
Click to expand...


It works!, now if I had any keyboard input... (The 6520 tested fine in my pet 2001 and the keyboard works perfect also, so I'm guessing the 74ls145 next, I just couldn't scrounge one up anywhere today.)



Later,
dabone
 
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Excellent! Hopefully it helps in further repair efforts with this machine. It would be nice to add a feature to the PETvet to act as a keyboard for a PET - having characters coming in over the serial port to work as key presses on a virtual PET keyboard. Adding to the wish list..
 
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