4040 dual floppy

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Kakemoms
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4040 dual floppy

Postby Kakemoms » Sat Jul 09, 2016 6:58 am

I just bought a 4040 and the obvious option is a Vic-1112 IEEE-488 cart. Schematics and ROM code are even available to build one.

An alternative is to buy a RS-232 to GPIB adapter, but that may require some not-so-obvious way to send commands to the drive. Has anyone tried that here and if so, what was the result?

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srowe
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Re: 4040 dual floppy

Postby srowe » Sat Jul 09, 2016 12:27 pm

I'd drop a line to dragos and see if there are any spare replica VIC-1112s left

https://www.kickstarter.com/projects/1203958506/vic-20-ieee-interface

If you go any other route you will need to transfer IEEE commands to the drive, that will mean writing your own LISTEN, TALK etc routines and then patching them into the KERNAL OPEN, CHRIN, CHROUT etc routines for external devices. This isn't straightforward but I've done this as part of my BASIC4 re-write.

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Re: 4040 dual floppy

Postby ral-clan » Sat Jul 09, 2016 3:09 pm

There is going to be a re-release of the VIC IEEE-488 cartridge, by the way:
https://www.kickstarter.com/projects/12 ... -interface

And....I just bought a SuperPET so if anyone knows of any IEEE-488 disk drives for sale for a reasonable price please let me know.

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Re: 4040 dual floppy

Postby eslapion » Sat Jul 09, 2016 3:27 pm

ral-clan wrote:And....I just bought a SuperPET so if anyone knows of any IEEE-488 disk drives for sale for a reasonable price please let me know.

It is relatively easy to convert a working 1541 drive into a 2031LP.

A few ICs and a GPIB female connector attached to one of the VIAs and a ROM change does it.

If you install a switchable ROM, you can easily toggle between 1541 and 2031 mode.

Use a 3 position switch with a 27C512 and you can have the 2031 mode, 1541 mode and JiffyDOS.
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Kakemoms
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Re: 4040 dual floppy

Postby Kakemoms » Sun Jul 10, 2016 2:20 am

srowe wrote:I'd drop a line to dragos and see if there are any spare replica VIC-1112s left

https://www.kickstarter.com/projects/1203958506/vic-20-ieee-interface

If you go any other route you will need to transfer IEEE commands to the drive, that will mean writing your own LISTEN, TALK etc routines and then patching them into the KERNAL OPEN, CHRIN, CHROUT etc routines for external devices. This isn't straightforward but I've done this as part of my BASIC4 re-write.


My immediate problem with a IEEE solution would be that it occupies the expansion port which I need for other things. So a 232 solution would enable me to have the expansion port free.

How large is your basic v4?

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Re: 4040 dual floppy

Postby srowe » Sun Jul 10, 2016 2:57 am

Kakemoms wrote:My immediate problem with a IEEE solution would be that it occupies the expansion port which I need for other things. So a 232 solution would enable me to have the expansion port free.


That's easiest solved with multislot expansion board. Granted they aren't easy to find these days.

It should be straightforward to drive the IEEE bus from the user port, that certainly seems to be what the RTC V-Link did. See here for my hunch.

How large is your basic v4?


The total code is just over 4K, however that includes

  • IEEE routines
  • intercepts for KERNAL routines
  • new BASIC commands

the first two alone should be less than 2K.

The original RTC ROM was 4K if you're happy with that the easiest thing would be to reverse-engineer the IEEE routines to figure out the wiring of their cable and use that.

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Re: 4040 dual floppy

Postby eslapion » Sun Jul 10, 2016 6:18 am

srowe wrote:That's easiest solved with multislot expansion board. Granted they aren't easy to find these days.

Jim Brain said he has a pile of VIC-20 multislot expanders in stock but they do have a slight mechanical configuration problem which, IMHO, is extremely easy to fix.

Kakemoms wrote:An alternative is to buy a RS-232 to GPIB adapter, but that may require some not-so-obvious way to send commands to the drive. Has anyone tried that here and if so, what was the result?

I have seen a lot of oscilloscopes and other specialized instruments connected to a PC in this manner and it works because the instruments themselves have routines in their firmware to support this sort of setup - my own Tektronix TDS-1002 does.

However, I have never seen a Commodore IEEE-488 drive used in this manner and I strongly doubt it can be supported.

Also, the max transfer rate I get is 19'200 bps but that may be the limit of my oscilloscope.
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Re: 4040 dual floppy

Postby Kakemoms » Mon Jul 11, 2016 3:23 pm

srowe wrote:
Kakemoms wrote:My immediate problem with a IEEE solution would be that it occupies the expansion port which I need for other things. So a 232 solution would enable me to have the expansion port free.


That's easiest solved with multislot expansion board. Granted they aren't easy to find these days.

It should be straightforward to drive the IEEE bus from the user port, that certainly seems to be what the RTC V-Link did. See here for my hunch.

How large is your basic v4?


The total code is just over 4K, however that includes

  • IEEE routines
  • intercepts for KERNAL routines
  • new BASIC commands

the first two alone should be less than 2K.

The original RTC ROM was 4K if you're happy with that the easiest thing would be to reverse-engineer the IEEE routines to figure out the wiring of their cable and use that.


IEEE on the user port? Well if it could be done without the 232, that would be better, but I doubt that is very straight-forward.

You make it sound like a multi-port expansion might be the best. I am a little worried about increased capacitance on the expansion port as my other projects tend to be.. sensitive to that. Maybe I need to think in terms of a through-port for the things I add. Thus make it possible to put a IEEE-488 on the outside of my own expansion.

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Re: 4040 dual floppy

Postby srowe » Tue Jul 12, 2016 12:15 am

Kakemoms wrote:IEEE on the user port?


IEEE requires 13 I/O lines, 8 for data, 5 for control signals. The top of the user port gives us 10 (PB0-8 + CB1 & CB2), there's other lines on the bottom (joystick, tape) that could be used for the others.

Well if it could be done without the 232, that would be better, but I doubt that is very straight-forward.


I'm not sure why you believe RS-232 to IEEE-488 would be a straight-forward conversion.

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Re: 4040 dual floppy

Postby Kakemoms » Tue Jul 12, 2016 3:48 am

srowe wrote:
Kakemoms wrote:IEEE on the user port?


IEEE requires 13 I/O lines, 8 for data, 5 for control signals. The top of the user port gives us 10 (PB0-8 + CB1 & CB2), there's other lines on the bottom (joystick, tape) that could be used for the others.

Well if it could be done without the 232, that would be better, but I doubt that is very straight-forward.


I'm not sure why you believe RS-232 to IEEE-488 would be a straight-forward conversion.


Oh well, we can believe what we want, but the idea came from the readily available 232 to 488 converters. But maybe we should differentiate between commodore-488 and GPIB-488 (like HP & NI are using) since it looks like a Vic-20 IEEE-488 only likes to talk to CBM equipment?

Anyway i have interest in getting 488 to 4040 working from the user port. I think I have seen others wanting that as well, so if anyone can make it, I have money in the bank. :wink:

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Re: 4040 dual floppy

Postby dragos » Tue Jul 12, 2016 6:48 am

Once all the kickstarter orders have been filled, there will be vic-1112s available. I anticipate 2 weeks or so and they will be built to order.

userport to IEEE is probably not going to happen, you'd need a custom kernal, someone to design it, etc. just use a cart port expander, they are cheap and give you many more options!
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Re: 4040 dual floppy

Postby srowe » Tue Jul 12, 2016 11:59 am

Kakemoms wrote:Anyway i have interest in getting 488 to 4040 working from the user port. I think I have seen others wanting that as well, so if anyone can make it, I have money in the bank. :wink:


Once I've finished my current project I'll have a look at the RTC ROM to see if I can fathom out the wiring. I'll need someone to help out driving the IEEE bus from an electrical level. It will need some sort of buffering but not the 3446s that the VIC-1112 uses.

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Re: 4040 dual floppy

Postby Kakemoms » Sat Jul 16, 2016 1:47 am

What is it with UK sellers? Had another one cancelling this order with the explanation:

"Hi, if you are from outise of you UK i wont be able to send it to you. There is a lot of restricions to send electronics that are so old :( i am not sure if thats not the reason."

That is after giving me a quote on the shipping, but being unable to ship and specifying the shipping cost. Basically I was not able to pay for the item, my address was outside of the area he had specified as shipping area. This has happened several times now, but only in UK.

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Re: 4040 dual floppy

Postby eslapion » Sat Jul 16, 2016 1:22 pm

dragos wrote:userport to IEEE is probably not going to happen, you'd need a custom kernal, someone to design it, etc. just use a cart port expander, they are cheap and give you many more options!

You don't necessarily need a custom kernal. Basic V4 resides in the BLK5 area and provides new commands and so does the Super Expander.

IMHO, if it was possible to have an IEEE bus on the userport, all that would be needed is a ROM cart which resides at BLK5. I strongly suspect the IO lines provided by the user port are not enough to do the job. The VIC-1112 carries 2 VIAs to do the job and I would assume it is for an important reason.

Added edit:
Looking at the schematics for the VIC-1112, it seems 3 8-bit ports are required to properly manage the Commodore version of the IEEE-488 GPIB and the user port offers only one.

Although in theory you could substitute all the DO-X VIA lines with a simple 74LS273 octal flip-flop, this still leaves the requirement for 16 communication lines while the VIC-20's user port can offer only 12 at the most, assuming you take over the joystick port lines.
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Re: 4040 dual floppy

Postby srowe » Sun Jul 17, 2016 3:45 am

eslapion wrote:IMHO, if it was possible to have an IEEE bus on the userport, all that would be needed is a ROM cart which resides at BLK5. I strongly suspect the IO lines provided by the user port are not enough to do the job. The VIC-1112 carries 2 VIAs to do the job and I would assume it is for an important reason.


The VIC-1112 requires 2 VIAs because it uses MC3446N transceivers. These are unidirectional so the line count is multiplied by two, one for Tx, one for Rx.

Using bidirectional transceivers like DS75160A/DS75161A would halve the number of lines required. The BASIC4 ROM you uploaded drives a single 6520 PIA so it is possible with less than 2 VIAs.


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