RE: CBM-HD

From: Baltissen, GJPAA (Ruud) (ruud.baltissen_at_abp.nl)
Date: 2004-07-06 13:21:56

Hallo David,


> You could do something like the 1541 does: Use a hardware 
> device of some sort to make the PET think......

I completely forgot about that. In fact I discussed this idea on June the
14th with Dirk Kleppke and Arndt Ívermann. In this case we used the SCH of
the 4040 as example 
<http://www.funet.fi/pub/cbm/schematics/drives/old/4040/320806-1.gif>.
The circuit left of UD2 really puzzled us and that's why I forgot about it. 

But because of your remark I also had a look at the one of the 2031: 
<http://www.funet.fi/pub/cbm/schematics/drives/old/2031/page-12r.gif>
But that one puzzled me as well: where is pin 11 of the 75161/UA1? This pin
is quite important for the transfer.

What really did please me was the fact that it also revealed that an active
ATN negates NDAC and NRFD. So one thing I can do at least whenever I detect
ATN is (L), is to negate NDAC and NRFD immediatly. 
Hmmmm, ATN is connected to ACKNOWLEDGE, the input that can generate an
interrupt. I could use it to perform this action. I have some doubts about
this idea but it is worth a try.

I don't mind to build a HW solution but I forsee two small problems:
- My first goal is to deliver a solution where no extra HW is needed. OK, a
cable has to be soldered anyway but IMHO there is a difference in soldering
cables or electronics (more psychologically then physically)
- This HW solution needs an extra output and all printerport ones already
have a vital function. This means I have to use another port as well, which
means more "hardware-stress" for the future user. 

If someone wonders why 64HDD can do the job W/O the hardware, I can give you
the answer. My CBM-HD is based on PC-Disk, an equivalent of Nick's 64HDD.
And I soon found out that the CBM is more time critical then the C64. For
example: originally I did actually collect the needed data for displaying
the directory AFTER receiving the TALK-command from the C64. And that was on
a 486/66. But a P3/450 was not fast enough as my 8032 timed out displaying
"FILE NOT FOUND?". So I had to change the program to collect the data
immediatly after receiving the actual command (as the 1541 does).


--
     ___
    / __|__
   / /  |_/     Groetjes, Ruud
   \ \__|_\
    \___|       URL: Ruud.C64.org




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