I spent some time reading the WD37C65C floppy controller datasheet last night. This floppy controller is found in the Outbound Laptop Floppy adapter circuit board. The board takes floppy commands from the host Mac compatible laptop (SE or Plus ROMs) and sends them to a PC standard Citizen floppy drive, and supports 1.44MB and 800K drives. I can't remember, but suspect 400K is supported as well.
Anyway, I noticed the 37C65 basically takes a set of floppy command words as input from the computer host and translates them into floppy drive actions, like moving the head in and out and finding sector beginnings and reading/writing data and such.
Which naturally led to wondering how the 37C65 is interpreting Macintosh floppy commands. Unless they're the same command set.
The NEC765 is kind of the great grand pappy of all floppy controllers, so I wouldn't be surprised if Apple/Woz used the same command set.
On the external floppy adapter board there's a 27C256 EPROM that could be acting as a command translater -- Mac command in on address pins, NEC765 command out on data pins. But the internal floppy adapter board completely lacks that EPROM.
Completely unrelated weirdness is that both adapters have a distinct 92C32 data separator on board, but the 37C65 incorporates an internal 92C32.
One of these days I'll have to trace out a schematic...
Anyway, I noticed the 37C65 basically takes a set of floppy command words as input from the computer host and translates them into floppy drive actions, like moving the head in and out and finding sector beginnings and reading/writing data and such.
Which naturally led to wondering how the 37C65 is interpreting Macintosh floppy commands. Unless they're the same command set.
The NEC765 is kind of the great grand pappy of all floppy controllers, so I wouldn't be surprised if Apple/Woz used the same command set.
On the external floppy adapter board there's a 27C256 EPROM that could be acting as a command translater -- Mac command in on address pins, NEC765 command out on data pins. But the internal floppy adapter board completely lacks that EPROM.
Completely unrelated weirdness is that both adapters have a distinct 92C32 data separator on board, but the 37C65 incorporates an internal 92C32.
One of these days I'll have to trace out a schematic...