16 Dec
2001
16 Dec
'01
10:27 a.m.
Richard Erlacher wrote:
Why? The WD37C65 is a much easier part to use, and it
programs pretty much like
a NEC uPD765, drives the cable directly, and automatically deals with the
data/clock separation for 500 KHz, 250 KHz, and 125 KHz data rates at both 300
and 360 rpm. You can lift 'em from broken HDC's or order 'em from
www.rocelec.com (Rochester Electronics). They're most common in PLCC-44, which
you should be able to handle, even if, like me, you didn't listen to Mom when
she told you to stop that.
It sounds like a nice chip. Since all I have is 3 1/2" 1.44mb drives I
will
have a fixed 500 Khz clock, thus less programing. Also the chips are
cheap
if you can find them $7.25 @ BG micro. I was looking some nec? chips at
Rochester
and they were over $75 each.
If you must use a WD part, which I prefer also, then
use a WD179x with a FDC9229. That does everything in
two chips, including
selecting the appropriate clocks. The 2797 uses an analog PLL and, unless you
are satisfied with a single data rate, that means multiple filters and analog
muxes, etc.
Thanks for the info. While a 2 Mhz machine would have been the speed of
system in the 80's I might as well go to 4 Mhz since the FPGA will run
that fast.
As a side note a 2 Mhz machine is about the same speed as a PDP-8. 1.5us
for a jump.
2.5 us for memory access.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html