Need HELP from hardware experts!

By edoz

Prophet (2444)

edoz's picture

29-09-2015, 12:18

Hi hardware experts! I need someone that have the skills to think about this.
It is not about MSX hardware but it is about CPC hardware. The thing is, in the MSX world we have a lot of nice cool hardware, like the DenyoNet, GFX9000, MP3 player, etc. which is not available on the CPC world so far. I think this is because less people are having the hardware skills in the CPC scene. I was just wondering what would it be cool to have the possibly to extent MSX hardware to the CPC world by making some kind of hardware slot adapter for the CPC computer.

I’m only talking about I/O based hardware. As the main difference is that the MSX is slot based and the CPC is RAM/ROM based, but for I/O based hardware that is not needed as it is pure I/O communication.

I wonder how difficult it would be to make such an adapter where you can put your MSX I/O based hardware in it. This adapter must power on the cartridge and give the cartridge the ‘feeling’ that it is inside a MSX computer and then there must be a way to communicate with the cartridge on I/O based way from the CPC computer.

If this is possible then the CPC will have a big benefit as it could use then MSX based hardware. The cool thing is that then more people can really use MSX hardware and therefor maybe hardware projects are more profitable and maybe more people will buy it. Other thing is that for example with SymbOS (as SymbOS is already platform in depended) more specific hardware applications can be created and that would be a benefit for all users.

I’m sure Prodatron will make a SymbOS GFX9000 version for CPC with network support if this would be possible. And that would be cool.. As a new apps created for SymbOS on the CPC can be used on the MSX as well!
As told I know nothing about hardware but does anymore think that would be possible. If you look to the layout of the PINs? Maybe this is very simple to create.

MSX Slot hardware PINS

CPC Expansion Port PINS

Login or register to post comments

By maxis

Champion (512)

maxis's picture

29-09-2015, 16:57

@edoz

The adapter is straight forward. CPC has unbuffered Z80. So, connect :
MSX slot ---- CPC slot
AB[15 : 0] to AB[15 : 0]
DB[7 : 0] to DB[7 : 0]
/IORQ-B to /IORQ
/M1-B to /M1
/RD-B to /RD
/WR-B to /WR
/EXINT to /INT
/BUSDIR - unconnected
CLOCK to PHI
/EXWAIT to READY
/RESET to /RESET
GND to GND
5V to 5V
+12V to generate from CPC 5V
-12V to generate from CPC 5V

You can also address the memories from Amstrad by adding a little decoding logic to wrap-up the address space.
Don't forget about the clock frequency of 4 MHz.

By edoz

Prophet (2444)

edoz's picture

29-09-2015, 20:00

That sounds that it must be not so difficult to do it ?..

As i'm not an expert is it just "connecting" the pins described above ? and taking care of the +12/-12 ?
The memories from Amstrad are not important for IO devices not ? So that is nice but not needed.
What do you mean about the clock frequency ? Do you need a generator to make a signal of 4 MHZ ?

By Grauw

Ascended (10605)

Grauw's picture

29-09-2015, 20:09

You can choose not to connect the +12/-12, although some cartridges require it. (If I recall correctly, either the MoonSound or Gfx9000 does, or both.)

By maxis

Champion (512)

maxis's picture

30-09-2015, 07:58

edoz wrote:

That sounds that it must be not so difficult to do it ?..

As i'm not an expert is it just "connecting" the pins described above ? and taking care of the +12/-12 ?
The memories from Amstrad are not important for IO devices not ? So that is nice but not needed.
What do you mean about the clock frequency ? Do you need a generator to make a signal of 4 MHZ ?

Well, not difficult at all. 4MHz instead of 3.57 will give you the audible pitch shift on any audio synthesis HW. Some really cool HW is memory mapped (SFG05)... And at 4.0MHz you can patch/re-use YAMAHA FB-01 firmware directly, IMHO.

Regarding the adapter, also don't forget to de-activate the following pins like that:

MSX SLOT:
/MREQ-B - pull via 1K to +5V
/SLTSEL - pull via 1K to +5V
/CS1 - pull via 1K to +5V
/CS2 - pull via 1K to +5V
/CS12 - pull via 1K to +5V

As you see, no active components are needed if you have no conflicting HW to be connected (address space)

By Prodatron

Paragon (1812)

Prodatron's picture

30-09-2015, 15:34

maxis wrote:

CPC has unbuffered Z80.

Could it be a problem that the CPC doesn't have bus drivers (it's just leading the Z80 pins to the expansion port)?
Anyway such an adapter would be crazy cool!

By maxis

Champion (512)

maxis's picture

30-09-2015, 23:46

Prodatron wrote:
maxis wrote:

CPC has unbuffered Z80.

Could it be a problem that the CPC doesn't have bus drivers (it's just leading the Z80 pins to the expansion port)?
Anyway such an adapter would be crazy cool!

1. Well, Z80 doesn't support more than 2 TTL loads per pin (since itself it is NMOS by nature). You could also notice, that the most of Japanese HW (disk controllers for example) used HCMOS logic for the address decoding.

2. No ribbon cable must be involved. The CPC to MSX cartridge interconnect must be as short as possible.

3. CPC's unbuffered bus will not work well with any HW, which clamps the logic HI below 5V (non-tolerant FPGA based MSX HW, for example).