MSX HDMI mutlimedia card

Hi, first sorry for bad english, but I do not think this last method is possible always. Of course this can work if you have something like:

ld a, something
out (0x99),a

It's easy to replace out(0x99),a to out (newaddress),a

the problem is register based access, out(c),xx inir, otir, ini, outi etc.

How can this simple code sequence be replaced?

ld c, 0x99
dec c         ; points to data port
ld b, 0x10
loop1:
outi
outi
outi
outi
djnz loop1
; after the loop i need to write an extra byte to data port, that is always 0x98. It's tricky, but i cannot rely on the 
; assumption that C is already holding 0x98. so i do not reload C with the same value and i simply do
out (C),c ;

at each outi, you need to figure what is THE CURRENT value of C register then change C to point to the correct address. you get problems:
- the sequence LD C, newaddress you inject causes timing problems on original z80
- C register is changed, you need to figure when to restore to its original value, because you do not know if the original sw rely on the original C value or always reload C.
- To know when to restore original register you need some smart behaviour that you cannot achieve with a simple hw logic. You need to understand the routine, something computers cannot do.
- if you inject some extra code to the original z80 one, its Program Counter gets also incremented. this can have side effects on relative jumps.

The hw address virtualization is attractive but i think can be done only on a FPGA z80 core when you can say
'virtual address A is physical address B' at the CPU / MMU level.

I agree, and now, i full understand. My problem is the insufficient knowledge of today's electronics. That's because while i've a solid base background of electronics, i've 'leaved' the pratical field 25 years ago. So, as you can understand, a relatively complex circuitry like the one you described seems to me too complex to worth the effort. This is because, 25 years ago, a thing like you described would required a lot of sequential/combinatory logic circuitry to be developed by hand...
(using flip-flops, logical gates etc.). Actually you can rise a lot the complexity by using a kind of somewhat imperative programming language and having those on the real metal. cool! (for my era).

Hello, Onno. Yes, certainly, any extension to the standard 9958 architecture is possible. On my side, I'm now fighting with the 99x8 simulated architecture to make sure, that it will be more-less cycle accurate from Z80 standpoint, but still will take an advantage of 166MHz SDRAM clock rate and asynchronous video interface running from 25MHZ (VGA) up to 1280x1024@162MHz. And the additional bandwidth is more than enough to add multiple transparent backplanes, tiles, sprites, etc....
Yet, the sacred problem is the SW/FW support, and someone will need to write the software to use these extensions.

However, personally, I'm more interested in expanding MSX software library by making the machine compatible with another gaming hardware. For example JAMMA ARCADE boards, having already Z80, SMS, NEOGEO, why not NINTENDO... The internal FPGA would be big enough to put 6502 + all the peripherals onboard.
For example, could be cool running "Prince of Persia" without the color clash on the good old MSX, of course for educational purposes only...

The plan is the following:
1. fully compatible 9918
2. Sega Master System/NEOGEO stand alone implementation
3. SCC+PSG (just to test the sound circuitry & TOSLINK)
4. fully compatible 9938/58
5. ...

Also, I prefer NOT TO REPLACE MSX by this card, but use your existing machine in conjunction with this card in a new context. It would be really cool to take an advantage of having 30 years old Z80 and running arcade native code on it. If single FPGA is not big enough to fit both 68000 and JAMMA graphics, then you can install two Procyon cards into the both slots and connect the cards together by HDMI link(for the fast data exchange). Many ways to have fun.

Well, in fact the main purpose of Procyon was connecting your MSX to the monitor via HDMI interface and extending video, sound and storage capabilities. However, if you would like to turn your machine into the fast internet terminal and to get any decent performance even when comparing to Raspberry thing, the one will have to design:
- PHP & Java HW interpreter;
- OpenGL compatible graphics controller.

Would it be still MSX?

I can program php and java but those are serverside. One would need to parse HTML/css on the MSX side (or PC proxy simplefying it to more MSX friendly files) if you want to browse.

I don't need to browse but a youtube player or skype client for MSX is possible and ofcourse MSX could have it's own www standard as far as page layout (and scripting) goes. The images/video is unavoidable.

I want my MSX to serve high resolution, the rest I can make myself once I retire