8 Apr
2007
8 Apr
'07
9:41 p.m.
Philip Pemberton wrote:
Hi guys,
I've just dug my not-even-a-tenth-finished floppy disc raw-reader out
of the cupboard, the plan being to finish it off.
That's weird. That's three of us separately suddenly fiddling with this again
(personally I suddenly stumbled across enough SRAM the other day for a raw,
over-sampled track buffer, which rekindled my interest in actually Getting
Something Done).
- All I/O lines from the floppy raised to +5V via
two 4k7 resistor packs
Hmmm, the SA-400 manual says that the lines should be terminated by 150 ohms
to +5V on the last drive in the chain. Output line 'true' from the drive is
logical zero, 0.0V to 0.4V, 48mA maximum. Output line 'false' is logical one,
+2.5V to +5.25V, 250uA maximum.
Doubtless the manual's available in electronic form somewhere on the 'net -
probably on Bitsavers.
I can step the head in and out fine, and the motor
seems to be spinning
(the drive's activity light is on at least). What I can't get is any
form of output from the drive - even /INDEX is stuck floating high
(FWICT it should pulse once for every revolution of the disc, i.e. about
once per half-second or so).
300RPM would be a 5Hz pulse rate, 360RPM would be 6Hz, so a bit more than that.
cheers
Jules