howard@brl-tgr.UUCP (05/05/84)
I wanted to add a three position switch to my apple drives. One position would write-protect the disk independent of the disk notch, one position would write-enable independent of the disk notch and the third position would allow the disk notch to function normally. This would be easy to do if one side of the disk notch microswitch was grounded or tied to +5V. To my great dismay, I discovered that the disk notch microswitch is not connected to ground or +5V. On page 146, Circuit Schematic: Disk II Analog Board, The DOS Manual, one side of the microswitch is connected to the pad marked W PROT and the other side is connected to WP RET. W PROT is wired to IC B4, pin 2 which provides the microswitch status to the digital card. WP RET is connected to the Phase 1 line. Does anyone know why the Phase 1 connection is made? Why isn't this side of the switch simply grounded or tied to +5? What would be the consequences of breaking the Phase 1 connection? Howard Walter howard@brl ...!decvax!brl-bmd!howard