Reset switch - will this work?

[necronom]

Just before I try this, I think it's probably a good idea just to check that I'm not about to do something really stupid!

Years ago I used to sometimes reset my C64 by putting a paperclip across the user port pins 1 and 3 (I think). Yes, dangerous, but I was 12. I also built in a mouse microswitch into a cable I made for the C64, which worked great.

Now I want one for my Vic-20. If I'm right, I can connect the left pin of the user port with the 3rd from left on the top row to reset.

Is this correct?

I'm going to solder the microswitch to the pins shown, then put electrician's tape over the other pins that are also sandwiched between the blue foam, so they should be safe from any unwanted connections in case the solder comes off, or something. I'll also be pushing against the foam, so it shouldn't put any stress on the solder.

And the other main question is will this make games like Ms Pacman work, as it sounds like it needs a reset to work.

[Noizer]

Hi necronom, reset button always good idea. Red marks on your pic is showing a connection from pin 1 (GROUND) to pin 3 (RESET), so it's showing right.
Some attention should be paid to pin 2 (+ 5V max. 100 mA // References: Programmieranleitung C64 - user port pinning seams vic 20 compatible). Keep avoiding to connect this directly to pin 1 (GROUND) or to any other of the pins!! Bad luck and it ends with fried chips. Short circuit. Take care.
Perhaps some other circuitry like resistor and capacitor would certainly improve the reliability and longevity of the beautiful vic hardware, but I can't argue with such simple "wire-only" connections, so I've always done that too and never seen anything weird hw/sw problem.
So what will happen on reset from mrs. pacman? Missing switch install, then check yourself

[srowe]

I had an (internal) mod like that on my VIC for many years. Somewhere I read that it was better to attach it to the 555 timer reset circuitry so I did that a couple of years ago. I can't find the explanation of why this is superior, someone else may remember the details.

[levoman]

The reason the 555 version is superior is that it takes time to reset and avoids the reset,reset,,,reset possibility that you get from just a switch!

with a proper mechanicaly de-bounced switch this is not a problem.

[chysn]

The reason the 555 version is superior is that it takes time to reset and avoids the reset,reset,,,reset possibility that you get from just a switch!

with a proper mechanicaly de-bounced switch this is not a problem.

What's the downside of reset, reset, reset?

[necronom]

Thanks everyone for the comments.

It works great. I've ordered some blue electrician's tape to make it look neater, and I'll put a "TOP" and "Vic-20 / C64 Reset" label on the top, then it should look half professional.

I put some heat shrink round pin 2 to isolate it from everything else.

This is it now, and I've got Ms Pacman running now after I did the reset

Also, any reason why my signature isn't showing up? I added one for a link to my Vic-20 YouTube videos, but it's not showing.

[Mike]

What's the downside of reset, reset, reset?

That partially depends on the kind of peripherals otherwise attached to the VIC-20.

First, the CPU requires the reset pulse to be at least two clock cycles long. A button bounce might easily produce an even shorter pulse than that at the end, leaving the CPU in a (temporary) inoperable state after button release. That should be curable with another reset button press, but it is a source of unreliability.

Longer gaps during the button bounce might irritate peripherals that have just begun their reset sequence.

Very early 6502s are suspected to take damage from reset pulses that are much too long, say >1 second. See here. The 555 circuit inside VIC-20 and C64 does a pulse of about 0.5 s, so that info has to be taken with a grain of salt.

...

Anyhow, I took care about those points with the latest design of the MINIMON cartridge - its reset circuit delivers a single, clean 2 ms reset pulse to the VIC-20 upon button release.