WIP: VIC-2020 MINIMON cartridge

[majikeyric]

Gorgeous !

[Mike]

Is the software already burned to chips? If not, I'd implore you not to do this:

MINIMON changes the BRK and NMI vectors, the latter one to keep itself and the BRK vector 'life' even when STOP/RESTORE is pressed.

There's no particularly good reason for the monitor to "rootkit" the normal STOP/RESTORE vector reset like this. I'd assume the custom BRK vector is set when the monitor is started anyway.

This is intended behaviour: on other CBM machines where the monitor is part of the KERNAL, it is the default action of the BRK vector to invoke the monitor break entry.

Otherwise, the NMI routine in MINIMON performs exactly the same actions as the VIC-20 KERNAL does, it services the RS232 subsystem and also honours the ($A002) warmstart entry of cartridges.

You can revert to the original BRK and NMI vectors with POKE783,4:SYS65234, this will also be documented in the manual.

[chysn]

This is intended behaviour

I didn't for a moment think that you accidentally included code that changes the BRK vector on NMI. I can just see myself getting frustrated, trying to restore vectors to normal in the normal VIC-20 way, and being thwarted. I don't see the rationale, and it seems like it might fall more into the "minor annoyance" category than the "feature" category. But you've been working with MINIMON a long time, and you've undoubtedly found it unobtrusive at worst and convenient at best, so I'm willing to trust that.

It’s just that you took pains to keep MINIMON out of the way in other respects, and taking control of a normal control mechanism seems to contravene that philosophy.

[Mike]

@chysn: PM sent

[Mike]

A new actor enters the play:



This chip goes into the ZIF socket of the MINIMON cartridge, as alternative to a 2716 EPROM.

The photo below shows the MINIMON firmware flasher in action:



Greetings,

Michael

[DarwinNE]

I would be interested, too. A kit would be OK for me, I can solder SMD components (apart extremely small ones and BGA's, of course).

[Mike]

I would be interested, too.

Thank you for your interest. The tests are still ongoing, but we're on the home stretch.

A kit would be OK for me, I can solder SMD components (apart extremely small ones and BGA's, of course).

SMT helps a lot to cut down costs for a series production, but IMO is not suitable as kit.

[DarwinNE]

SMT helps a lot to cut down costs for a series production, but IMO is not suitable as kit.

No problem at all!

[crusti]

Any news / price on this, is it still available?

Ive been after a VIC for a while, finally got one coming and would love to learn 6502. Learned z80 and C thro the years but the vic was my first love.
Had a bash on 6502 on a C64 then got into Amiga.

This look like it could be right up my street.

[Mike]

Any news / price on this, is it still available?

MINIMON is not yet available for purchase.

Currently, there exist two prototypes (of the kind you're seeing here) and they work fine as is. However the BLK5 inhibit function - which is used to suppress the autostart of the slave cartridge - has shown to be somewhat cumbersome to use. That part of the PCB is under thorough redesign and will be tested next month. It replaces the simple reset button and the BLK5 inhibit jumper by a more versatile reset button and a timer circuit that does a 'normal' reset upon a short press, and a 'freeze' reset (which temporarily inhibits BLK5) upon a longer button press.

[Brad]

Expressing interest

[Mike]

Expressing interest

Thank you. There's still work in progress towards the intended hardware design so it will take some time until I can announce its general availability, so please bear some patience with me.

I also put a response into your inquiry thread in the "Buy, Sell and Trade" section.

[majikeyric]

Any update Mike ?

[Mike]

Any update Mike?

Yes. The design of the PCB is finalised and it also includes the 'freeze' reset I had mentioned in another thread. This freeze reset (initiated by a longer button press and indicated by a blue signal LED) inhibits the autostart by temporarily blocking the BLK5 select line going to the slave cartridge.

Unfortunately, the pilot run of the PCBs suffered from a fabrication flaw in yet another (but otherwise already tested working) part of the circuit, so I'll have to wait until after the Xmas holidays for further commissioning. Sorry.

Greetings,

Michael

[majikeyric]

That's very interesting,
it will be really top notch