io ports.

[Andy Rea]

is there any hardware add on or otherwise, that uses port $FF (a0 - a7 high) or do they all use the partial decoding where a combination of one or more address lines are low ?

reason i ask is i want to use port $FF for something, as long as all exsisting hardware needs at least one of the address lines low i should be ok.

reagrds Andy.

[sirmorris]

I always refer to the source code to eightyone.

these are the ports which are read from:

0x07, 0x41, 0x43, 0x45, 0x5f, 0x73, 0x77, 0xbf, 0xdd, 0xf5, 0xfb:

these are the ports which are written to:

0x07, 0x0f, 0x1f, 0x3f, 0x5f, 0x73, 0x77, 0xbf, 0xc7, 0xcf, 0xd7, 0xdf, 0xdd, 0xfb, 0xfd, 0xfe:

[Andy Rea]

Coolio

suppose it could always be changed if it causes problems.

Regards Andy

[sirmorris]

Use it 'for something' eh?

COME ON! You can't tease us like that! taint' fair!

[Andy Rea]

Just thinking ahaed, i'd like to be able to control ( enable / disable ) some extra features in the next ULA design, i've gotten hold of a 100 pin lattice device, mounting it is going to be a challenge ! 0.5mm pitch leads but it does have 68 io's where as the altera desing i'm currently working on is a 44 pin device and doesn't have enough io's so i've cheated and used a 16v8 aswell, now the altera chips have arrived i've checked the pin spacing and am now doing a final check of the PCB layout before getting a couple of prototypes made.

regards Andy

[Prime]

Just thinking ahaed, i'd like to be able to control ( enable / disable ) some extra features in the next ULA design, i've gotten hold of a 100 pin lattice device, mounting it is going to be a challenge ! 0.5mm pitch leads but it does have 68 io's where as the altera desing i'm currently working on is a 44 pin device and doesn't have enough io's so i've cheated and used a 16v8 aswell, now the altera chips have arrived i've checked the pin spacing and am now doing a final check of the PCB layout before getting a couple of prototypes made.

It should be possible, even for home made PCBs to mount that device, one of the next round of prototypes this end is a TQFP-100 xilinx device, same pitch as your altera one, however I'm also trying with the PLCC84, sockedted and another with it mounted direct to the board, it is pretty tight in the ZX81 case but I think that I should be able to make it fit, obvuiosly we want a solution that will fit in the case and is easyest to assemble....

In the pictures further up the thread you'lls see my test board also has an internal RAM expansion that is plugged into the 28pin RAM socket, I have thested and this deffo fits in the case, and has socketed RAM and a 74LS00 on it, so the ULA design should fit if you bend some of the resistors and caps flat.

BTW I think there are some good videos on youtube re: mounting flatpack devices by hand, the main thing is getting them aligned before soldering, don't wory too much about bridging pins, as long as you have some solder wick to remove it.

Cheers.

Phill.

[Andy Rea]

burger.... load and save routines have OUT ($FF),A in them...

what about $7F ???

regards Andy

[sirmorris]

Hmm, that makes me think my foolproof plan of looking at the EO source is not so foolproof

I think that you would be fine going with 7f. I've bagsied port 7 ;¬)

Put it this way - if anyone gets a ULA replacement then has problems with their peripherals all it would take would be a quick recompile of the verilog

Got with 7f and be damned, that's what I says.