Before I start...my apologies for my long rambling. Sometimes my mind just pours out on the keyboard...good or bad. lol
So, I have a Mojo V3 FPGA development board and I've gotten a few VGA signals in the past. I also have an ATF1504 CPLD (thinking about using the ATF1508) that I wanted to use for glue logic and possibly VGA.
I'm just learning programmable logic so I have a ways to go. But my earlier tests with the FPGA board were promising (using VHDL).
I'm curious on what you guys think. I'd like the following in my design:
1) 65C816 (4-8 MHz depending on complexity)
2) VGA
640x480 for 80 column mode.
320x240 "fat pixels" for 40 column / color modes (think C64 style graphics)
Direct access like the Apple IIe.
3) 512K RAM (maybe another 512K for video RAM)
4) 128K ROM (maybe more??)
5) Video must be generated in parallel with the CPU access (like the Apple II does) so that maximum video access is possible. I know this is more complicated with the '816 (which is why I have you lovely people to offer advice.
)
Now, I know this is a complicated system. But keep in mind I don't care if it takes another 25 years. I'm in no hurry. This is the computer I want.
So back to my question....I don't think the 1508 could handle all of this. So I was thinking of using TWO of them. One for glue and smaller functions and the other for video. But if I'm going to have two large CPLD's (and I have a LITTLE bit of experience with FPGA's), why not just use an FPGA and be done with it?
However, I don't want to use some giant FPGA that I cannot solder by hand (no reflow). My soldering skills are pretty good but my eyes are going to put TQFP-100 at the upper limit. Maybe TQFP-144 if I get a good microscope. But that's pushing it.
I'm not about creating a Woz design that uses minimal chips. But I don't want to be wasteful at the same time.
What do you guys think? FGPA for VGA and CPLD for glue? FPGA for it all? 2-3 CPLD chips?