Sid-20 mod for the Vic

[yoyodyne]

Ok, sorry for the delay. Here is what vic-cart pin to connect to
what sid pin. I wish I had a good circuit drawing program.
(any free ones out there?).

You should check out the sid appendix in the c64 ref guide
to use a guide.

Sid 6581______Vic-20______Cart Pin
Pin #_________ Cart Pin____ Signal
**********************************************
1 2200 pF capacitor, connect to sid pin 2
2 see above
3 2200 pF capacitor, connect to sid pin 4
4 see above
5 ............X ................RES
6 ...........V ............... S02
7 ...........18 ..............CR/W
8 ............T ...............I/O2
9 ...........B............... CA0
10 ..........C............... CA1
11 ......... D ...............CA2
12 ...........E ...............CA3
13 ...........F .............. CA4
14 ...........Z ..............GRND
15 ...........2 ............... CD0
16 ...........3 ................CD1
17........... 4 ................CD2
18 ...........5 ............... CD3
19............6 ................ CD4
20............7 ................CD5
21 ...........8 ............... CD6
22 ...........9 ................CD7
23 n/c
24 n/c
25 ......... 21 ............. +5 volt
26 n/c
27 Audio out, not on vic-20 cart
28 +12v External source, not on vic-20 cart

[GreyGhost]

For Pin 27, could you audio out with a female RCA jack and use a Y cable and your video cable to run the sound off the speaker in the monitor?

[yoyodyne]

There is a transistor and capacitor there first, before the
rca plug. See the c64 ref guide schematic for the 64. I copied
what the 64 has connected to pin 27. I am not sure what
quality of sound, or possible damage to the sid, directly
connecting the sid to an external source might have.

I really need to draw a diagram....

[ral-clan]

A diagram would be helpful, but thanks for sending what you have so far. I am amazed at how simple it is (this is good for someone like me).

Now to find a SID chip. Anyone have an extra they can sell me? (or trade for VIC stuff).

[yoyodyne]

I was thinking, it would be possible to add a 2nd sid at I/O3, and
then you could have stereo!

Also (this relates to the paddle problem thread): The sid does
the paddle input duties on a 64, so the hardware is already installed
on the sid-20 board to add a second pair of paddles for the vic. Pins
24 and 25 are pot x and pot y.

I did this on mine, to see how well it worked compared to the
vic's own input. And it was better, but only slightly. The 64
ref guide talks in the appendix about interfacing a sid chip, and says
a higher value capacitor may help "jitters". I haven't tried that yet,
but in looking at the 64 schematic, the 64 has more circuitry to
multiplex the sid chip to 2 control ports.

[Jogi]

Hi Ruud,

If you want something like a cart, you can forget it. The 6502 outputs its address line directly at the expansion port, just like the 6510 in the C64. But, unlike the 6510, the 6502 cannot be tri-stated. End of the story.

see the Superpet with the Trick can 6502 tri-stated.....

Regard Jogi

[damnstraight]

If you are looking for a free circuit board drawing program, look here. Its decent, and if you like you can have the boards made.
http://www.expresspcb.com/

[adric22]

I see this thread has been dead for a few months, but it is the first time I've seen it. It is a neat idea. I am wondering if you have it linked with the audio output of the VIC chip? That way, heaven forbid, a musician could write a tune to use the 3 SID voices in combination with the VIC voices. wouldn't that give you 5 voices total?

Also keep in mind there is a microcontroller SID replacement available now so you don't have to cannibalize a real SID.

Wouldn't it also be cool to add better video to the VIC-20?

[ral-clan]

Technically you would get seven voices. Four VIC voices (including noise channel), and three SID voices. Another voice if you make the speaker to go onto the user port.

[shem]

Sorry to bring a 2 year old thread alive but has anyone actually done the sid add on for the vic20??

yoyodyne have you got a schematic yet?

[yoyodyne]

Well, I think I drew it out on paper, but didn't upload it.

It is really simple, just follow the pinout description, and
run some traces to the appropriate cart pin.

I wasn't happy with the audio quality, so I need to work on that some.
I was running it through an external speaker.

I was thinking about using a 8580 sid, which only requires
9v vs. 12v, which might be easier to get from a vic.
Not from the cart port, but I would like to add the sid inside.


-Brian

[smj]

Interesting for sure. So, you were basically running the SID's audio
through the VIC-20's sound line and then out through the AV port? I
would think having direct audio out would be best, but you would need
to amplify the signal and filter off the DC. I'll look closer at the details.

If you could also still have the 3 voices from the VIC's chip, you probably
could run the output of that on the input of the SID and make use of
the SID's filter.

[Jeff-20]

smj, your avatar needs to be on the front page in full size.

[matsondawson]

For Pin 27, could you audio out with a female RCA jack and use a Y cable and your video cable to run the sound off the speaker in the monitor?

I'm confused. In the n schematic it shows an audio in on Y, just next to CA13. Is it not really there?

[shem]

One oher thing that I just thought of is the clock signal it shouldnt be a problem as long as both the c64 and vic run on the same clock speed but I cant remember now I will have to have a look later