FAL6567 back-burner project

[John West]

Have a look at the C64 schematic. It's far more complicated than you'd expect.

For what is proposed, you need every address bit from CPU writes to be visible on VIC pins. A8-A11 are connected directly (through the bus that goes to ROM and colour RAM). A0-A5 and A8-A13 connected through the multiplexers U13 and U25.

The problem is A6 and A7. VIC does output them. They get multiplexed with A14 and A15 (from CIA2) through U15, but that's a one-way trip. The CPU's values can't be seen by VIC.

The lower bits of the ROM and colour RAM address (including A6 and A7) go from VIC through U26, but that's one-way too.

And you still need A14 and A15 for bank switching to work. VIC doesn't see them either.

[rrossi]

Was this project ever finished? Curious as to whether this is in a working state.

[ElEctric_EyE]

rrossi wrote:

Was this project ever finished? Curious as to whether this is in a working state.

I guess Rob could answer. Maybe Rob is on Vaca? His last post here was back in July 2018. His last entry into the FAL6567 Github repository was 6 months ago. I hope he's OK. Maybe Dr. Jefyll can let us know how he's doing?

[GaBuZoMeu]

Rob is posting frequently on AnyCPU.org

[ElEctric_EyE]

GaBuZoMeu wrote:

Rob is posting frequently on AnyCPU.org

That's great! I forgot about that sister site... Maybe rrossi should shoot him a PM from over there...

[Rob Finch]

I still exist. I'm busy working on another project - FT64, posting on anycpu.org. But I still check 6502.org a few times a week. Although I haven't said much recently. I had wait about 2.5 months for parts

[ElEctric_EyE]

Nice to hear from you Rob... I see you've devoted some time to the FAL6567 on GitHub. What is the current status of this core? Is it abandoned?
It is a very complicated IC. Someone's dreamchild from MOS. That's not to say it's bad however...

[Rob Finch]

Picked up this project again, yup after four years. Progress is being posted on anycpu.org.

Most recently switched output to HDMI. Improved timing generation. A composite output might be available via a four-bit resistor DAC.

Came to realize that tripling up on the CAS signal cannot be done as the VIC-II uses reversed row and column addresses.

Trimmed out the cpu and math processing, for now.

[Rob Finch]

Finally got a prototype PCB made, but there are several errors on it. When I converted symbols in KiCad I did not notice that KiCad automatically changed the power connections. That means that several of the chips would be powered from the wrong source. This can easily be fixed on the board by bending the power pins out from the socket and wiring them up to the correct power source. Four chips are affected. There is one other wiring error, connecting CAS instead of RAS on one pin. I have since fixed these things in the schematics.

I hope to have a board built up within a few days, but I am still waiting for parts.

[Rob Finch]

Got TQFP32 adapter boards in the mail today. It was one piece to assembling a prototype. Breaking out an adapter board I had a look at it and was confident I would be able to solder to it although it would be difficult. Then I got the part out to solder. Well, dang it. Either I ordered the wrong part, or the wrong adapter board. The part is about ½ the size of the footprint on the adapter board. There is no way to mount it. I checked the packaging TQFP32. I am guessing I picked the wrong part number.

I managed to solder a socket to the PCB but I was having trouble focusing my eyes.

The 74xxx06 IC is on back-order for October 2023. So, this project moves along at a snail’s pace.

[Sean]

Rob Finch wrote:

The 74xxx06 IC is on back-order for October 2023. So, this project moves along at a snail’s pace.

That sounds very frustrating. Is there a shortage across all the 74-series families, or just the specific families that meet your needs? I've seen 7406 and 74LS06 chips in stock from at least one place recently.