13 Jun
2010
13 Jun
'10
2:53 p.m.
On 13 Jun 2010 at 22:33, Phill Harvey-Smith wrote:
Wouldn't that have been handled within the disk
controler chip WD177x,
WD[1,2]79x or whatever, could be determined by counting the index
pulses and the time delay between them.
On the WD 17xx controllers, there's a "Force Interrupt" command that
allows for interrupts on several different conditions, one of them
being index pulses. So an RPM check would have been simple to
implement, assuming some sort of timer/counter was available.
I've got a 1978 floppy controller here that uses about 55 ICs, one of
them being a WD1781. A fair amount of the board is taken up by the
data separator--it was designed by a guy whose last job was designing
read channels for the ISS 3330 clone.
--Chuck