[net.micro] Apple disk drive question

howard%brl-bmd@sri-unix.UUCP (10/31/83)

From:      Howard Walter <howard@brl-bmd>

	Does anyone know why one side of the write protect switch is
connected to the phase 1 motor line? I expected it to be grounded. 
Reference: DOS Manual page 146 - the write protect microswitch is
connected to the pads marked W PROT and WP RET. Thanks

Howard Walter
howard@brl

zben@umcp-cs.UUCP (11/02/83)

[..]
Why does write protect switch connect to motor phase 1?  So the DOS can
test for write enable?  How else would it know not to try to write?
I recommend a close comparison of the controller and disk schematics from
the DOS manual with a copy of "Beneath Apple Dos", with particular
attention to the coding sequence given for "testing write protect"...
Ben Cranston       ...seismo!umcp-cs!zben       zben@umd2.ARPA