Now if the HDMI spec is mainly to select an appropriate FPGA that you know will allow you to do HDMI later on, that's a valid point.
Absolutely it is. I don't want to mess around too much swapping FPGAs as I develop - I'd rather get the 'end game' FPGA, and learn from the ground-up on that. I'm assuming, of course, that there's no real reason I can't develop a VGA output on a dev board with HDMI fitted? Or offer VGA
AND HDMI as outputs on the final version, for example?
Yeah Lattice is the 3rd biggest player in the FPGA market. They specialize in being lower cost than the big leading two. Tho the tools on Lattice are not quite as good while still flowing the same free basic version and expensive as hell full version scheme.
Purely out of interest, is there anything on the expensive-as-hell full version software that a beginner like me would want?
Since the cost of the chip is not that high of a priority for you you better stick to Intel or Xilinx as they have better tools. Personally i enjoy Intel/Altera tools the most and i really like the Qsys/SOPC builder tool that wires up your digital computing systems auto-magically.
The cost is still a priority, just not quite as high as the factors before it in the list.
The only thing holding me back from the MAX 10 series is the cost of the evaluation board, but I can stretch to it if needs be - I just want to make sure no-one's going to pipe up after I've ordered one with a comment along the lines of, "
Haven't you checked out the Costmin LogicBlaster IV? It does everything you want, packs 200KB of RAM, makes the tea and takes your dog for a walk and the dev board includes HDMI and VGA and only costs £50..." Because that would make me cry...
Oh, I also meant to say that I have no preference for VHDL over Verilog at all - it's just that the only exposure I've had to FPGA code is via Grant Searle's Multicomp code, which is in VHDL, hence I've spoken about VHDL in this discussion but don't mean to exclude Verilog. I'm right at the start with this project, so I am ultimately extremely flexible in which path I take.
Previous Altera MAX series tended to be 5V tolerant but the MAX10 not anymore. Then again if your chips are TTL it will all work on 3.3V signals just fine as long as there are resistors to limit current, or you can just use a single 8bit logic buffer to do it proper since the data bus is only 8 bits wide anyway.
System Interface Considerations:ALL the chips in my computer that would connect to the FPGA are either 74HCT buffers for data / address / most command signals, or the CMOS Zilog Z80 itself for a couple of control signals (and these will be going TO the Z80 FROM the FPGA and are active-low with 5v pull-ups on them).
The only area for potential variation is in the address bus (from the MMU), which
may have HCT, HC or LS logic driving the extended address lines.
You still get the around 600 to 700Mbit serial IO performance so HDMI should be just fine, but having 90KB of internal block RAM is going to be quite expensive on it.
The
10M50 is the most attractive proposition, I think, with 200 KB of RAM in it.
For a start just look around at what dev boards you can get from the vendor you like. Be prepared to pay $50 and up for a decent one (But sometimes >$100). The decently sized boards always have some form of SRAM or SDRAM or DDR2 on them. HDMI tends to be rare but if it has VGA its probably good enough for now as you can likely add your own HDMI port later on. (Remember you want to first learn how to use these FPGAs so start simple)
Well, the 10M50 is available on a dev board with HDMI on it. That would provide me with a good hardware example to work from and all I'd need to worry about would be getting the FPGA set up properly to display something on it. I could always wire up a VGA socket as well and go that path first. It's
darn expensive though.