20 Feb
2010
20 Feb
'10
9:41 p.m.
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