RE: Unexpected IRQ behaviour on a VIC-20

From: Baltissen, GJPAA (Ruud) <>
Date: Sat, 29 Jul 2017 10:39:22 +0000
Message-ID: <>
Hallo Marko,

> The obvious solution would be to communicate via shared memory. ...

Every test has its own identification. If an interrupt occurred, this code is written to a variable. If a test reads the correct code in this variable, then it knows that the interrupt has been executed as should (or not). That  works fine so far. I'm thinking about copying the IFR to another variable as well before it is reset by reading the A or B port.

What am I doing? I am creating my own tools to test the VIC-20 and C64. Indeed inventing the wheel twice but I have my reasons for it:
- the sources and schematics are free, as always.
- the idea is to use the same sources for a cart version and for a Kernal ROM replacement version.
- the two main reason for a new VIC-20 version
  - I had a VIC-20 that appeared broken but had a faulty video circuit. So the idea rose to connect LEDs to the userport: the first thing the program does is letting the user know through these LEDs that the computer is not dead.
  - I wanted a Kernal version. But the original code is a real mess. So I decided to write my own, not only for this reason but also for the fun and learning curve.
- the three main reason for a new C64 version:
  - the C64 tool uses extra ICs to test things. I prefer to keep it more simple by only making connections between existing pins.
  - the tool starts with using a subroutine when the RAM hasn't been tested at all !!! If the RAM is indeed broken, the tool simply won't work.
  - same reason as above.

Because I need the userport for the LEDs, I have to use another wiring scheme than the original tool. But if you want to have such a tool and cannot buy it (or what ever) then IMHO you have to solder your own set. Then why not choose to solder one that comes with free source codes? :)

Met vriendelijke groet / With kind regards, Ruud Baltissen

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Received on 2017-07-29 11:00:02

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