Ah finally I can read my mail again. Couldn'tb read it for the last three 
weeks due to network renovation and maintenance.
Hope I didn't miss anything send to me.

>BTW: The DPU is an 8MHz clock crystal, with an XOR gate (I think -
>could be a NAND, its been a while) acting in its non-linear mode to
>generate the clock pulses.

It's three INVerters instead of XOR gate.

>Circuit diagram? Or was Dean's one the one?

I made a gif picture of my DPU. Is it allowed to send it to list ?


Some additional info:

SAM drive with amber LED is a normal 800K drive
SAM drive with a red LED is a 1.44M drive

The drive led of the 1.44 drive stays on because of a disk controllor 
flaw.

Drive LED burns whenever the the MOTOR ON signal is active. The FDC
turn it off after a number of index pulses have passed. When no 
floppy is inserted the drive doesn't produce index pulses. Once a 
disk is inserted the FDC can count the index pulses and the LED goes 
off.
 
On a 800K drives the LED only burns when the motor on signal is 
active and a disk is inserted.

FDC Command &D0 (Forced interrupt, terminates any command in 
progress).
This Command is used at the start of most disk routines to check if 
theres a disk in the drive.

Edwin Blink. 

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