Date : Mon, 09 Feb 2004 22:53:48 -0000
From : "Chris Thornley" <C.J.Thornley@...>
Subject: Re: Discs
Hi,
I found this article I published to the list a while back about floppy disk
units available. Attached is a very small circuit I found in png format of a
40 to 80 track stepper.
Chris
-----Original Message-----
From: owner-bbc-micro@... [mailto:owner-bbc-micro@...] On
Behalf Of Chris Thornley
Sent: 06 August 2002 14:08
To: 'Dawn and Austin'; bbc-micro@...
Subject: RE: [BBC-Micro] Using 1.44Mb HD Floppy drives with a Master 128
Importance: High
Hi,
Shuggart Disk drives 3.5 inch
There are 5 types of 3.5 inch drive
(1) The Quad Density Floppy (2.88MB) (1.44MB) (720KB)
(2) The Standard High Density (1.44MB) (720KB)
(3) The Tri or Multi Mode High Density Floppy (1.44MB)
(1.2MB) (720KB)
(4) The Standard Low Density Floppy (720KB)
(5) Very Old Single Sided Disk Drives
Type (1) Is a Quad Density Floppy Drive which operates at 300rpm and has
three transfer speeds.
Type (2) Is a standard high density floppy which operates at 300rpm and has
two transfer speeds.
Type (3) Is a Tri mode high density floppy drive which operates at 300rpm
and 360rpm and has two transfer speeds.
Type (4) Is a standard low density floppy which has one transfer speed.
The high density drives contain a optical or mechanical media sensor which
instruct the drives to the correct transfer speed to operate in.
Therefore if you insert a high density disk into a drive it will switch into
its high speed mode. Disks can be fooled by placing some tape over the high
density notch but they wont be as reliable as standard low density floppies.
Shuggart Disk Drives 5.25 inch
There are 4 types of 5.25inch drive
(1) The High Density Floppy (1.22MB)
(2) Low Density 80Trk 96Tpi (720KB)
(3) Low Density 40Trk 48Tpi (360KB)
(4) Very Old Single Sided Disks Drives
Type (1) Is a High Density Drive which can operate at 300rpm and 360rpm and
has two transfer speeds.
Type (2) Is a Low Density 98Tpi drive which can operate at 300rpm with one
transfer speed.
Type (3) Is a Low Density 48Tpi drive which can operate at 300rpm with one
transfer speed.
On 5.25 drives if you put a logic 1 on pin 2 they should resort back to
there 300rpm modes and conversely a logic 0 will be 360rpm high density.
The Attached Document has connection details for the shuggart interface some
of the pins have neumours uses depending on if the manufacturer has obeyed
the standard or if the correct jumper is set.
Also the newer drives will be operating slightly faster than there older
cousins so they might be missing pulses and therefore you will have to alter
your keyboard links.
The 40 80 track problem Watford DFS required a *FX command to implement
double step and Solidisk DFS required a *dblestep command. If your drive has
no double step switch. I have found a circuit if anyone interested which has
details of these modifications for the 40 80 Switching unit.
Thanks
Chris
filename="PC Floppy.txt"
Connections to PC drive (34 pins Shugart bus)
The connector for the power supply consists of 4 pins:
pin 1: 5 volt
pin 2: Ground
pin 3: Ground
pin 4: 12 volt
It is important not put this connector in the wrong way. You probably
will wreck
your drive !!! Normally it should be very difficult to do this, but I
can assure
you it can be done. Just try it out with the power off and see for
yourself
which way fits best. By the way I read that for the 5.25 inch drives
with the
bigger connectors pin 1 is 12 volt and pin 4 is 5 volt !!
I checked out some books and magazines to give you some detail on the
drive
connector. Only the even number connections are used for signals. The
odd
numbered pins are connected to ground.
PIN 2: DISKCHANGE Output signal. This is a tricky one to start with.
It is
used for a number of different signals by each manufactorer. The first
one is
the most widely spread used. DISKCHANGE is perfect to use for the amiga
diskchange signal. HIGH DENSITY/DOUBLE DENSITY input signal to switch
drive
motor between 300 and 360 rpm. Only used for 5 1/4 inch floppy drives.
IN USE
input signal for letting the drive know something is coming up soon.
Also used
for driving led at front of the drive. HEAD LOAD input signal for the
drive to
put the head to the disk and pre magnetise it. (Rarely used)
PIN 4: IN USE Another pin use in more ways than one IN USE is the
most likely
candidate. see pin 2 (Sometimes you can have DISKCHANGE and HEAD LOAD).
With
internal Amiga drives IN USE is always connected to the MTRX signal. So
when the
motor is spinning the LED is on.
PIN 6: DRIVE SELECT 3 see PIN 10. Pin 6 is sometimes used for the
READY
signal (see PIN 34).
PIN 8: INDEX output signal will be low when the magnet on the
flywheel of the
drive passes the Hall sensor (when drive SELECT is low).
PIN 10: DRIVE SELECT 0 input signal for selecting the last drive
which is
then connected to this line. You will have to get the drive jumpers set
to the
drive select you want. Normally the drives are left with the jumper on
SELECT 0
and the cable is twisted to change select lines (Yes that's why there is
a
twist).
PIN 12: DRIVE SELECT 1 see pin 10
PIN 14: DRIVE SELECT 2 see pin 10
PIN 16: MOTORON input signal switches to motor on. Sometimes the
amiga way of
switching on the motor with DRIVE SELECT can be set with a jumper on the
drive.
PIN 18: DIRECTION SELECT Input signal. When low stepping direction of
the
head is to the axis (inside) of the disk. High is to the outside of the
disk.
PIN 20: STEP Input signal. With every low pulse the head is stepped
to the
next (by pin 18 determined) track when the drive is selected.
PIN 22: WRITE DATA Input signal. Here the data to be written on the
track is
coming in from the computer.
PIN 24: WRITE GATE Input signal. When low the data from pin 22 is
written on
the disk.
PIN 26: TRACK 0 Output signal. When the head is above the first track
this
line will be low when SELECT is active.
PIN 28: WRITE PROTECT Output signal. When the write protect hole is
open
(disk is write protected) and SELECT is low this signal will be low.
PIN 30: READ DATA Output signal. When SELECT is low then the data on
the
track is written to this line.
PIN 32: SIDE 1 SELECT Input signal. When the SELECT is active this
line set
the head (upper or lower) on which side is selected.
PIN 34: READY Output signal. Low when SELECT is active and the disk
is
spinning at the right speed (INDEX signal) or, in a older simpler
version, if a
disk is in the drive. It tells the computer that the drive ready to do a
read or
a write of the track. The signal is high when the drive is empty (no
disk), when
the motor isn't running or the motor is running too slow. Also very
shortly
after a Head step signal it is high (15 ms). You see in this way the
drive is
not mounted by the amiga! (Rarely used as DISKCHANGE or IN USE).
filename="40_80_TR.png"
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