6 Nov
2007
6 Nov
'07
2:50 a.m.
I'm going to add some to my own topic. The questions below still
stand, but I've got more info! : )
I want to use a QUME 842 or SA800 in an altair disk
subsystem.
Both seem to have the same interface.
The FD400-5x0-5x1 manual seems to show the drives being quite similar.
The first thing I see is that there are extra signals.
"Trim Erase", "Write Enable", and "Write Data" where the
Shugart
interface only has "Write Data" and "Write Gate". I assume that
gate and enable are the same thing. The FD Pertec drives also have
"IN", "OUT", and "STEP" instead of "STEP" and
"DIRECTION", but that
is not a big deal. That can be generated in software.
What I don't see is any input to perform the function of head
current. How does the shugart interface handle this?
Can I ignore the trim erase feature? How do I generate a write busy
signal? I'm willing to make some circuits to fake these signals if required.
More info:
The pinout of an Altair disk drive...of the wires connected. Omitted
pins are either not connected, power, or ground. All lettered
connections are ground.
6 - Output - Door Open (IDOP
7 - Head Current Switch (IHCS)
8 - External Trim Erase (Option) (IEEN)
9 - Input - Write Enable (IWEN)
10 - Input - Write Data Input (IWDA)
11 - Input - Step In (ISTI)
15 - Input - Step Out (ISTO)
16 - Input - Head Load (IHLD)
17 - Output - Index (IINXP)
18 - Input - Drive Motor On (IDEN)
19 - Track 0 (ITRK0)
20 - Output - Read Data Output (IRDA)
One thing that interests me slightly more is the possibility of a
regular 3.5" disk connected to the Altair. I don't care about the
encoding or format being compatible with a standard controller.
It is very similar, but is also a soft sector disk/drive. How close
is close? Can I just use a microcontroller with a timer to time from
one index to the next and divide it up into 32 sectors? Will this be
close enough for the Altair? Anyone know what kinds of errors I
would get? A microcontroller running at 16MHz would be able to count
between pulses with 16MHz/1 accuracy. With the SA800 I would have a
sector hole sensor giving me the correct timing.
There still is the issue of the write trim erase feature, whatever that is...
Any comments or ideas on the idea? Is it worth trying? I've got a
very weird tarbell card that formats and uses 3.5" disks as a 70k
mini floppy. I guess anything is possible. : )
2 - Density Select (/REDWC)
8 - Index (/INDEX)
10 - Motor Enable Drive 0 (/MOTEA)
12 - Drive Select 1 (/DRVSA)
14 - Drive Select 0 (/DRVSB)
16 - Motor Enable Drive 1 (/MOTEB)
18 - Direction Select (/DIR)
20 - Head Step (/STEP)
22 - Write Data (/WDATE)
24 - Floppy Write Enable (/WGATE)
26 - Track 00 (/TRK0)
28 - Write Protect (/WPT)
30 - Read Data (/RDATA)
32 - Head Select (/SIDE1)
34 - Disk Change/Ready (/DISKCHG)
I'm not going to sleep a wink tonight. I hate having ideas at 10PM... : (
Grant