| That's not quite true.
The 1770/1772 have some built in motor control logic.
Type I commands on 179X use bit 3 to control head loading (1=load).
Type I commands on 177X use bit 3 to control the whole motor startup
sequence (0=enable spin up).
The type II settle delay (bit 2) is 30 ms, not 15 ms.
Write commands use bit 1 to disable precompensation.
Step rates are 2, 3, 5, 6 ms (r[1..0] = 00, 01, 10, 11).
The status register is also slightly different.
Bit 177X 179X
7 Motor on Not ready
6 Write Protect Write Protect
5 Type/SpinUpOk Type/WriteFault
4 RNF RNF
3 CRC CRC
2 TR0/LostData TR0/LostData
1 DRQ/Index DRQ/Index
0 Busy Busy
There is a myth floating around that the part is a special
one. This isn't true. The part is ordinary, and it is in the newest
Western Digital daa books.
I, by the way, don't have a data book. I have a copy of some of
the pages from a data book I found in an office at SRC in
Palo Alto.
Just call Western Digital and ask.
|