16 Dec
2005
16 Dec
'05
12:07 a.m.
Chuck Guzis wrote:
On 12/15/2005 at 6:01 PM Allison wrote:
Pin21 can be at DC, Pin19 can be slower than 4mhz it's unknown how far
that can be pushed. The RDW signal on pin22 must be correct for the
media (RDW is Read Data Window and its the recive clock). The only
reason that write clock must be present on read is to keep the write
logic alive as a clock splices (glitches) on the write clock can cause
the write counters to burp and crud can come out during write. It's not
part of the read logic.
Think of the read and write logic as being mostly seperate like in a
USRT like COM2601. Then add a custom ucontroller between them and the
bus to do stuff.
Save for wrtclk controls that pin21 not the clock
on pin19
Ya got me, Allison! Pin 21 it is. Curious thing that it must be present
to READ also, according to specs. So, what's the lowest clock speed I
could run the 765 at and still be assured of reading 8" FM? Back when I was still doing floppy controller design,
it was the 1781,
which doesn't divorce write clock from the master chip clock.
True of all the WD parts. Very unlike the 765. I found that people that
worked with either found the other a bit jarring to teir thinking when
they switched. Not so much right or wrong just plain different.
Allison