Sinclair ZX80 / ZX81 Forums

[XavSnap]

Hi,

http://zx81.ordi5.free.fr/brico/iocards

I can poke an address, but i had to type CLS to peek an input !
We had to force the /RamCs, but can i set the RomCS to 1, directly on the zx bus?
I had to but my Pcb on this chat as soon as.

[RWAP]

Hi - so I take it this is a new card?

What format is a djv file? Any chance you could upload a picture?

[siggi]

Try http://www.caminova.net/en/downloads/download.aspx?id=1

Siggi

[siggi]

Hi,

http://zx81.ordi5.free.fr/brico/iocards

I can poke an address, but i had to type CLS to peek an input !
We had to force the /RamCs, but can i set the RomCS to 1, directly on the zx bus?
I had to but my Pcb on this chat as soon as.

Perhaps Wilf's io circuit could be used as example:
http://www.user.dccnet.com/wrigter/index_files/ZXRAMIO.htm

Siggi

[sirmorris]

I used that design for MMC board #1, it works well.

[siggi]

I used that design for MMC board #1, it works well.

Using also the address $FFFF?

IMHO i/o via $FFFF results in a collision with the last byte of the last ram mirror (/RAMCS decodes 16-32K and 48-64K) and destroys also the byte at $7FFF. I recommend to use an address in ROM address space (/ROMCS decodes 0-16K and 32-48K). Then the rom mirror can be disabled by pulling /ROMCS high (via a diode, see Wilf's schema) to avoid a conflict with the rom when the i/o ports are written/read.

Siggi

PS: Pulling /RAMCS high disables only the internal ram, not any external ram pack and does not help in this case.

[sirmorris]

No. I used the zx97 IO board's decoding scheme.

[XavSnap]

Hi,

I will try to force the /RomCS on the zx connector via a diode.
Thanks !

[siggi]

But you have also to change the address decoder to decode an address in the rom address space 0 to 16K or 32 to 48K!

Siggi

[XavSnap]

Hi,
I will try it!
But, is there any conflicts with the /M1 (???) ?
(i don't what is this famous /M1 ! )
Have Fun.