RE: 1541IDE and 1541IDE-S
Date: 2007-12-12 08:33:57

Hallo Jim,

> but I thought I read somewhere else you felt the 
> 16 bit IDE circuit was to complex.

Not for me:) No, it is I just like to keep things simple so that other, less gifted people can solder it as well. I actually built a board with the 16 bits design some years ago but the first reaction was: "WOW, very nice. But that is a bit too complex for me :(".

About your design: CS1 of the IDE bus is not not needed AFAIK. That I used it in my designs was for the simple fact that other designs used it as well and I wasn't that familiar with the bus. So far things run fine without using it so one could think about discarding it.

> ... and I think I may have turned it into a 8/16 bit design ...

Pure curiousity: why didn't you use the SCH I sent you as base?
For every one else:

> as you need to shift the addresses to the IDE channel <<1,
> My idea is to shift all the address lines up by 1, using A0
> to determine whether one wants the low or hi byte.

Sorry to say, but this is a very bad idea IMO. At this moment I store several parameters, like the size of the disk, the start of the directory and the link to the next sector, as four bytes in a row. Copying them to disk can be done like this:

  ldx #3
1 lda LBA0,X
  sta IDE_reg,X
  bpl 1
With a shifted address a more complex routine is needed.

That's why I used this scheme:
A0..3 : basic IDE registers
A4    : choosing CS0 or CS1
A5    : high/low byte
When I started with the 8 bit design, I could use a lot of the original 16-bits sources as I only had to drop everything conneted with A5. 

> Since I gate the 74LS42 line through 1 more level of logic, it 
> might require ALS or H variants for the '139, '244, and '00 parts.

No, IDE is very forgiving.

Regarding the debug port: I'm busy with soldering two intelligent HP 7-segments displays to the free A port of one of the 6522's. It should display POST codes while everything is working. In this way I can see what part of the Kernal it is executing. In the future the ports of the other 6522 can be used as we don't need the ....

WOW, no kidding, the house on the other side of the street is on fire !!!!!

.... need this 6522 anymore as we can get rid of the drive.

Hallo André,

> The problem is the PET memory map

Eh, Jack was reffering to the 8250 which is drive IMHO, not a computer.

OK, that was just a quick reaction. I'm having another MCSE course this week which means quite some studying in the evening, so I don't have much time for other things. Sorry for that but I'm sure you understand.

I have to go again... :(

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