20 Feb
2010
20 Feb
'10
6:43 a.m.
the was posted to a amiga ircchannel some time ago,
http://www.softpres.org/glossary:kryoflux
Looks interessing, if there will be better drivers and accessable info
for writing or chaning the code on it, drive situation cant be much worse
than what we have with the catweasel.
Regards
--
Jacob Dahl Pind | telefisk.org | fidonet 2:237/38.8
20 Feb
20 Feb
11:16 a.m.
Jacob Dahl Pind wrote:
the was posted to a amiga ircchannel some time ago,
http://www.softpres.org/glossary:kryoflux
Looks interessing, if there will be better drivers and accessable info
for writing or chaning the code on it, drive situation cant be much
worse than what we have with the catweasel.
As I see it, there are several issues:
- No useful documentation! Not even a description of the output file
format.
- Software is a binary blob, like everything the SPS have ever
released. They "intend" to release the sources, but I'm not holding my
breath.
- No I/O buffering. Wiring a TTL or CMOS I/O straight to a floppy
drive usually doesn't work very well. Moreso if your I/Os are 0V/3.3V
LVTTL or LVCMOS instead of 0V/5V TTL/CMOS. Voice of painful experience
here...
It's nice, and its release can only be a good thing. What I'd like to
see is the price tag...
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
1:41 p.m.
New subject: Buffering - was Re: alternativ to catweasel
On 20 Feb 2010 at 19:16, Philip Pemberton wrote:
- No I/O buffering. Wiring a TTL or CMOS I/O
straight to a floppy
drive usually doesn't work very well. Moreso if your I/Os are 0V/3.3V
LVTTL or LVCMOS instead of 0V/5V TTL/CMOS. Voice of painful experience
here...
On the subject of OC buffering, please forgive a related question.
I'm sitting here looking at the specs for the Pertec tape interface,
which appears to call for a 38 ma OC output drive current. I assume
the original intended driver is a 7438.
I'd like to use a denser package to keep the parts count down.
I've been looking at the 74F760 octal OC buffer, which appers to have
the moxie to do the job, but is a relatively uncommon part.
Would it be possible to use a more common darlington instead, say, a
ULN2803? The thing that bothers me is the t(on) and t(off) timing,
quoted at a max of 1 usec. Is it really that slow?
Thoughts welcome!
--Chuck
21 Feb
21 Feb
10:28 a.m.
New subject: Buffering - was Re: alternativ to catweasel
On 20 Feb 2010 at 19:16, Philip Pemberton wrote:
That could well be right -- or is it? IIRC the normal termination for
Pertec interface lines was a 220R to +5V and a 330R to ground. Which
gives Thevenin equivalent of a 3V source with a 132R internal resistance.
So you need to sink about 22mA. That might be a little easier...
- No I/O buffering. Wiring a TTL or CMOS I/O
straight to a floppy
drive usually doesn't work very well. Moreso if your I/Os are 0V/3.3V
LVTTL or LVCMOS instead of 0V/5V TTL/CMOS. Voice of painful experience
here...
On the subject of OC buffering, please forgive a related question.
I'm sitting here looking at the specs for the Pertec tape interface,
which appears to call for a 38 ma OC output drive current. I assume
the original intended driver is a 7438. I'd like to use a denser package to keep the parts
count down.
Any particular reason why? I wouldn't have thpught it was much more work
to solder a pair of 14 pin DIPs (2 off '38) rather than a single 20 pin
device (I asusme that's the pacakge of the '760). If you don't need
gating in the final bufffers, can't you use the '06 or '07, which would
give you 6 signal drviers in a 14 pin package?
I've been looking at the 74F760 octal OC buffer,
which appers to have
the moxie to do the job, but is a relatively uncommon part.
Would it be possible to use a more common darlington instead, say, a
ULN2803? The thing that bothers me is the t(on) and t(off) timing,
quoted at a max of 1 usec. Is it really that slow?
I could beleive it was. Darlingtons are slow, particularly at turning off
(I beleive it's having to dump the charge from the base of the second
transistor. There are various tricks to improve things, but they're only
applicable if (a) you can make a connection to that base and (b) you have
a -ve supply rail available (more -ve than the emitter of that second
transistor). The first certainly doesn't apply to the ULN2803.
-tony
11:12 a.m.
New subject: Buffering - was Re: alternativ to catweasel
On 21 Feb 2010 at 18:28, Tony Duell wrote:
Any particular reason why? I wouldn't have thpught
it was much more
work to solder a pair of 14 pin DIPs (2 off '38) rather than a single
20 pin device (I asusme that's the pacakge of the '760). If you don't
need gating in the final bufffers, can't you use the '06 or '07, which
would give you 6 signal drviers in a 14 pin package?
It has to do with dedicating the real-estate to what amounts to 26
open-collector outputs (by ignoring some options, I could get it down
to 24). That's 7 7438's. I may go with using the 7407s, though. At
least they're commodity and easy to find if they need replacing. The
package count (5 vs. 4 for octal buffers) difference is negligible.
Since there's going to be only one controller per drive, I could also
revert to plain old totem-pole output buffers as well, as the
controller will probably be mounted right on the drive with only a
few inches of cable. That broadens the array of choices
considerably.
Looking at the specs, you're right--the termination is 220/330.
--Chuck
5370
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ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
classiccmp＠philpem.me.uk -
rachael＠telefisk.org