6 Sep
2010
6 Sep
'10
8:21 p.m.
On 7 Sep 2010 at 3:26, Philip Pemberton wrote:
Depends if the capture mode has auto-retrigger. Some
PICs implement
capture/compare by storing the timer value and throwing an interrupt
on an external event. The timer is left running -- IIRC there isn't an
option to reset it after the C/C event.
As long as the timer is either wide enough (e.g. 32 bit) or wraps to
0 from its maximum count, it really doesn't matter. AVRs definitely
do wrap and so do a number of other chips. ARM uses a 32-bit timer,
which is more than adequate for floppy use.
Point taken. But the SMSC floppy controller is a bitch
to find, and if
memory serves it has issues with precompensation (if it's anything
like modern controllers, it just plain doesn't do precomp). Totally
worthless for anything vaguely resembling reliable R/W work.
The FDC37C78 is still listed in SMSC's current production, but I"ll
agree that it's not easy to find on the spot market. It does have
selectable precompensation (port 3F4):
http://www.smsc.com/media/Downloads_Public/Data_Sheets/37c78.pdf
It even does FM uncomplainingly.
--Chuck