Commodore Amiga A500 Technical Reference Manual page 10

15 TKO*
16 DKWEB*
17 DKWDB*
18 STEPB*
19 DIRB
20 SEL3B*/
Not Used
21 SEL1B/SEL2B OC
22 INDEX*
23 + 12V
Note: * in signal name denotes active low signal.
External Disk Connector Identification Mode
An identification mode is provided for reading a 32 bit serial identifi-
cation data stream from an external device. To initialize this mode,
the motor must be turned on then off. See pin 8, MTRXD* for a
discussion of how to turn the motor on and off. The transition from
motor on to motor off reinitializes the serial shift register.
After initialization, the SELxB* signal should be left in the inactive
state.
Now enter a loop where SELxB* is driven active, read serial input
data on RDY* (pin 1), and drive SELxB* inactive. Repeat this loop a
total of 32 times to read in 32 bits of data. The most significant bit
is received first.
7
I/0 Asserted by selected drive
when read/write head is
positioned over track 0.
OC Write gate (enable) to drive.
OC MFM output data from
Amiga.
OC Selected drive steps one
cylinder in the direction
indicated by DIRB.
OC Direction to step the head.
Inactive to step towards
center of disk (higher
numbered tracks).
OC A500: Select drive 3/A2000:
Not used.
A500: Select drive 1/A2000:
Select drive 2.
I/O Index is pulse generated once
per disk revolution, between
the end and beginning of
cylinders. The 8520 can be
programmed to conditionally
generate a level 6 interrupt to
the 68000 whenever the
INDEX* input goes active.
160 ma maximum; 540 ma
surge.