VIC 1112 IEEE Interface

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Re: VIC 1112 IEEE Interface

Postby Kakemoms » Sat Dec 17, 2016 4:08 pm

eslapion wrote:It's the opposite.

The MOS6522 IRQB can only drive low or do nothing at all. The 65C22 or R65C22 can drive low or high. This way you can connect more than one 6522 to the same IRQ line and this is done in many pieces of equipment. If a 6522 pulls low and a R65C22 pulls high then you have a tug of war between the two.

A diode may do the job but it has to be extremely fast and have a very low voltage drop. The 1N6263 I use on the Behr-Bonz DRL 'AND' gate should to the job.

A 10kOhms pull-up resistor will definitely not.

Thanks Eslapion. I didn't have that diode, but I managed to get it to work with a 1N5814:


At least the R65C22 works for my Vic-20 and its keyboard. Unfortunately it didn't work for the IEEE device. I got the same problems as with the MOS 6522. E.g. "Load"$",9" loads the directory but displays nothing (unlike the original Vic-1112 which shows it):


I will test more another day. Maybe there is a strange bug in the software or something about the R65C22 in this configuration.

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Re: VIC 1112 IEEE Interface

Postby Kakemoms » Sun Dec 18, 2016 8:56 am

Short update: I moved the two MOS6522 from my Vic-20 into the IEEE interface and I get the same result. With two R65C22 in the Vic-20 (with the IRQ diode modification) I have keyboard and serial read/write (towards my Commodore 1541) working as before.

The program starts as usual (with SYS45065) and the EPROM verifies as being the same as the image you released. I will burn a new EPROM (with the original VIC-1112 image) and test if it works with that one.

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Re: VIC 1112 IEEE Interface

Postby dragos » Tue Dec 20, 2016 2:16 am

Please keep me informed of your progress. I suggest trying real mos 6522s, maybe you have a 1541 lying around you can borrow them from.

I test each board thoroughly prior to shipment (read/write and burn in) and this is the first issue not related to user soldering error I have had.

very curios to put the issue to bed and see you have a working card.

0110 0110 0110 The number of the beast...

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Re: VIC 1112 IEEE Interface

Postby orion70 » Tue Jan 17, 2017 2:23 pm

Any news about the ETA for this interface? It's been a while since the Kickstarter campaign was closed...

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Re: VIC 1112 IEEE Interface

Postby Kakemoms » Tue Apr 18, 2017 2:15 pm

Just to follow up on this; I have just tested the cart with an original Vic-1112 ROM image. The SYS45065 starts the software, but I can not LOAD, format (PRINT#15,"NO:...) or SAVE to the disk. The original Vic-1112 cart works with this drive and can do all that, so there is something wrong with the cart.

I will try to re-flow the solder in case its just a poor connection. I am also a little unsure about some of the via holes as they do not seem to contain metal (or maybe they don't have the solder mask opened). It could of course also be one of the IC's, but I don't have any of these (except for the 74LS00N) here, so I can't check that easily.

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Re: VIC 1112 IEEE Interface

Postby Kakemoms » Wed Aug 30, 2017 10:35 am

This has been long overdue, but I was able to test the MC3446N ICs that were used on my VIC1112 board using an IC tester that I built from these instructions. Quite cheap once you get the parts from ebay. If you decide to make one yourself, add this to the database for the 3446 test:

Code: Select all


Anyway I found that two 3446s were dead and have ordered replacements. My 4040 is currently dead, so until I fix the drive I will not be able to test the VIC1112 with it, but I assume it will work. Anyway, the IC tester is nice to have around! I gave it some steroids with an MEGA 2560 board to get more pins (up to 32):

Testing 3446 works.. if it works!

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Re: VIC 1112 IEEE Interface

Postby norm8332 » Thu Aug 31, 2017 9:59 am

Thanks for the link for the tester, I have everything except the zif socket. Looks like a cool project.

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