MSX H8 (CPU) cartridge

Por st1mpy

Paladin (900)

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15-02-2010, 15:25

There is this old web site that shows a design of a H8 CPU/microcontroller cartridge design for MSX. (All in Japanese, but there are schematics and pictures there)
www.nana.or.jp/~hiramats/h8/msxh8.html

And there is another web site that shows some applications for it, like 3D renderer and some graphics effects. (It doesn't show properly on most web sites, but I downloaded the mpg data from there.)

You hear some people talk about this sort of cartridge design often, but this one is a working design. It would be cool to build it, but the H8 CPU doesn't seem to be easy to get hold of outside of Japan.
Replacing that with something more readily available like Atmega microcontrollers would be an idea, but they don't support external RAM (internal is between 1KB to 8KB I think. And for this H8 design they got 1MB....)

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Por PingPong

Prophet (4093)

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16-02-2010, 19:13

Uh? what is this cart? and what's is purpose? it has a h8 mcu. But what the use? the MCU works in parallel with z80? or is a co-processor?

Por st1mpy

Paladin (900)

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16-02-2010, 20:41

did you check the videos in the link above? they show a 3D renderer working on the H8, and being drawn through the VDP in MSX. And there is another video of some graphics effects processed in H8 and drawn through the VDP in MSX.

The guy lists other practical use like these:
- playing or recording PCM samples (using the A/D, D/A converter on H8, with the data on 1MB Ram on the cartridge),
- a sound effector (taking the sound output from the MSX into the H8 cart and process it with effects and put it back to the MSX through SNDIN),
- as an extra processor (it is working in parallel with the Z80 so you can off load work to it),
- RS232 interface,
- BMP/JPEG/PNG graphics loader (decode them on the H8 cart, convert to MSX's format and pass it to MSX),
- a font manager (do some font management, overlaying over graphics etc),
- 3D polygon engine (this one was actually done and is one of the video above, he calls it Chlorella Project.
- sound cartridge
- put a video out in the cart to avoid transfer to vdp
- etc...

Por Leo

Paragon (1236)

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17-02-2010, 11:00

is it a bit like Z380 extension ?
i think if you start doing an extension based on atmega there is poor chance of re-use of
the code on h8 or Z380 ...
the only interest xould be to demonstrate the feasability , but they already did on H8?
I think we should think about first a comon API , an interface for these extensions , the
konamiman unapi specs are quite good for that . after it is open to use any solution like
fpga / H8 / other copros
i think it is interesting to take a mcu very available , at the same time is it possible to find
a very available cpu with Z80 native code , people can re-use their knowledge of Z80 , you
can port more existing apps to make them run faster : you dont start from zero.
...
Z380 card might be a bit expensive and maybe today you can find much faster device for
lower cost , is it possible to build a fast z80 co-pro like H8 ?
...
i see interface are based on 82C55 , so it is IO based , i think a shared 16kb ram page
would be faster, or there is maybe a trick in this H8 design .

Por Leo

Paragon (1236)

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17-02-2010, 17:20

hitachi as merged with mitsubishi for ICs , now it is called renesas , the H8 3048 mcu is still listed :
http://www.renesas.com/fmwk.jsp?cnt=h83048_root.jsp&fp=/products/mpumcu/h8_family/h8300h_series/h83048_group/

Por st1mpy

Paladin (900)

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17-02-2010, 17:42

This is what it says on that guy's site about access:
---
The MSX-H8 cartridge is not on Z80's I/O space but in the memory space. So, to access with machine code you don't use IN/OUT commands but the LD command. But obviously you need to make the slot that the MSX-H8 cartridge is in accessible with BIOS's ENASLT etc. (You can read/write byte by byte with RDSLT or WRSLT, but ENASLT will be faster.)

Between MSX and the H8, there is a commonly used IC for parallel interface called 8255. (MSX also have equivallent IC to 8255). If you open either page 1 or page 2 of the slot that the MSX-H8 cartridge is in with ENASLT, for page 1 you can see the 8255 on address 04000H-04003H, and for page 2 you can see the 8255 on address 08000H-08003H. (Actually the upper bits of the address bus is not decoded, so if you look at 08004H-08007H or 0BFFCH-0BFFFH you would see the same.)

...
---
The above is from here (just the first 2 paragraphs, there are more info there.):
www.nana.or.jp/~hiramats/h8/msxh8man/access.html

H8 is still quite easy to obtain in Japan (quite a few comes up if you search online), but exact model this guy used might be hard to obtain.

Por PingPong

Prophet (4093)

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17-02-2010, 19:20

did you check the videos in the link above?

yes, what was unclear to me was the interface between the cpu and mcu.
If, i've understood correctly, the z80 can comunicate with the cart through the memory mapped i/o address, and IS not able to see the cart memory as a ram slot. True?

So i think in the the video for the demo the z80 work is to download the rendered image from the cart and upload to vram, right?