CIA Question for FPGA Experts

[Plaz]

CIA chips are a common failure on amiga motherboards. I was wondering how much work would be involved in recreating CIA chips in FPGA for classic repairs. With pin out differences, I'm pretty sure a piggyback board would probably be needed. I'm thinking it could revive lots of 1200's and 4000's (maybe some CD32s). Perhaps even another version for 3000's.

Plaz

[amigadave]

Isn't this what Jens is doing with CloneA, replacing all custom chips, one at a time with either fgpa, or other parts that will eventually be recreated in new silicon?

[downix]

Don't see why it would be that difficult.  How about I mess with the MiniMig's limited CIA's and see if I can expand them to full complience?

[Plaz]

Isn't this what Jens is doing with CloneA

Sure but that's a whole new machine with the entire machine probably in one big FPGA. This would be a much smaller project just for patching classics.

Plax

[Plaz]

@downix

Don't see why it would be that difficult. How about I mess with the MiniMig's limited CIA's and see if I can expand them to full complience?

Awesome if you could use minimig as a headstart. Minimig CIA should be similar to those used on A500/2000/3000. I don't know if the surface mount versions on A1200/4000 are different.

Plaz

[downix]

Plaz wrote:
@downix

Don't see why it would be that difficult. How about I mess with the MiniMig's limited CIA's and see if I can expand them to full complience?

Awesome if you could use minimig as a headstart. Minimig CIA should be similar to those used on A500/2000/3000. I don't know if the surface mount versions on A1200/4000 are different.

Plaz

Not internally, no.  Incidentally, the C128 had a CIA as well.

[Plaz]

Not internally, no. Incidentally, the C128 had a CIA as well.

Same as the ones in Amiga? I might have guessed it would be like the one used in the C64, but functionally a bit different than the ones in Amiga. Interesting if they all used the same design just in differnt packages.

Plaz

[Zac67]

Well, even the C64 had two CIAs, (older) 6526 (same with C128). 8520s even work in C64s, they're just faster and have additional timer(s).

The 1541's 6522s were just called VIAs (simpler, but very similar still).

Are 8520s hard to get? Vesalia has them in stock for 6.90€ (DIL) or 3.90 (PLCC) - no way to beat that price with an FPGA!

[Plaz]

@Zac67

Thanks for the CIA lesson. Interesting about using 8520's in even a C64.

Are 8520s hard to get? Vesalia has them in stock for 6.90€ (DIL) or 3.90 (PLCC) - no way to beat that price with an FPGA!

I saw that today also. I wonder how their stock is holding up. Has any one made CIAs in 10 years?

Plaz

[downix]

Plaz wrote:
@Zac67

Thanks for the CIA lesson. Interesting about using 8520's in even a C64.

Are 8520s hard to get? Vesalia has them in stock for 6.90€ (DIL) or 3.90 (PLCC) - no way to beat that price with an FPGA!

I saw that today also. I wonder how their stock is holding up. Has any one made CIAs in 10 years?

Plaz

Don't think so, but I'm studying the MiniMig's one as we speak so who knows.

[Belial6]

@Downix

You know, I'm really looking forward to seeing something come out for the MiniMig from you.  Almost every time you post, you sound like you really know what you are talking about.  Instead of just telling people to forget it, you will point out the difficulties, and frequently give advice on how to over come the challenge.  This lends to your credibility.  Unfortunately, I, like most, have become very skeptical over the years, so I will withhold judgment until I see something tangible.  I am particularly interested in seeing your MiniMig external bus.  It would be great to add another name to list of people who have delivered on the MiniMig.

[downix]

Belial6 wrote:
@Downix

You know, I'm really looking forward to seeing something come out for the MiniMig from you.  Almost every time you post, you sound like you really know what you are talking about.  Instead of just telling people to forget it, you will point out the difficulties, and frequently give advice on how to over come the challenge.  This lends to your credibility.  Unfortunately, I, like most, have become very skeptical over the years, so I will withhold judgment until I see something tangible.  I am particularly interested in seeing your MiniMig external bus.  It would be great to add another name to list of people who have delivered on the MiniMig.

If you'd like I could post the schematics now, it's getting the PCB bits done that I drag my feet on.

[FrenchShark]

Zac67 wrote:
Well, even the C64 had two CIAs, (older) 6526 (same with C128). 8520s even work in C64s, they're just faster and have additional timer(s).

The 1541's 6522s were just called VIAs (simpler, but very similar still).

Are 8520s hard to get? Vesalia has them in stock for 6.90€ (DIL) or 3.90 (PLCC) - no way to beat that price with an FPGA!

The difference between the 6526 and 8520 is the TOD (time of day) counter.
It is a 24-bit counter on the 8520 and a BCD counter on the 6526.

The ECS/OCS Amigas have a 1 MHz capable 8520 (running at 0.7 MHz) and the AGA Amigas have a 2 MHz capable 8520 (running at 1.4 MHz).

[AeroMan]

I have a sugestion. It may not be possible, but it needs to be analyzed first before saying it is or not.
What about using a microcontroller ? There are some really cheap and fast ones in the market. Microchip just released their new PIC32. It has a MIPS core and runs at 75Mhz.
I believe it could be done with something smaller than this one. Microcontrollers seems a good alternative to replace the CIAS

[freqmax]

@AeroMan:
I think any MCU will suffer from latency.
As for a suitable chip. Because the amount of logics way less a CPLD might be more suitable. They might even come in 5V ready version.
There's also the Spartan-3A which uses internal EEPROM to store the configuration.