Disk on my NIC-80

From: Dwight Elvey <elvey_at_hal.com>
Date: Mon Apr 10 18:39:27 2000

ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
> > two sector holes. It uses a 74121 one shot to detect
> > this signal. The resistor and capacitor give the following
> > timing: 0.7 ( 0.22e-6 * 22e3 ) = 3.4 ms. I would think
> > that this signal would be about 3/4 of a sector to
> > catch the index mark in the middle. As I recall,
> Yes, that sounds reasonable. The monostable triggers on each sector hole,
> but as it's non-retriggerable, it can't retrigger on the index hole (well,
> not after the first revolution, possibly). And 3/4 of the sector time
> would be a reasonable value to aim at.

 The circuit is clever. The output of the '121 goes to
the data pin of a '74. Both the '121 and '74 are clocked
by the index pulse. If it is the index and not the
sector pulse, the output signal of the '121 gets clocked
through the '74. If it is just another sector pulse,
the '121 has timed out and the output of the '74 doesn't
 I was looking at the Athana site. Has anyone dealt with
them? How much do they charge for a box of 10 8-inch disk?
Is anyone planning on making a purchase soon, they have
a $100 minimum?
Received on Mon Apr 10 2000 - 18:39:27 BST

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