Apple Lisa - Disk Data Storage

Confidential
Lisa Hardware Reference Manual
The
I/O Block controls the transfer of data from the 6505 to the
disk. The transferred data is in a buffer located at $00C501 -
$00C7FF on the 68000 side and at $0200 - $03FF on the 6505 side of
the shared memory. The 68000 can use the MOVEP instruction to
transfer this data from the shared memory to its main memory.
DISK DATA STORAGE
Data is stored in 512 byte blocks on the floppy disk. The number of
blocks in a track depends on the track number. A block is equivalent
to a DOS 3.3 sector. The total capacity of each side of the disk is
868 blocks or 444,416 bytes.
Track number
o - 3
4 - 9
10 - 16
17 - 22
23 - 28
29 - 32
33 - 38
39 - 45
THE JSR COMMAND
Blocks in track
23
22
21
20
19
18
17
16
The JSR command ($84) transfers control from the normal RWTS routines
to another program. This program can be located in the ROM, or can be
downloaded into the shared memory and then executed. The ~wo bytes
after the command byte ($00e003 and $00e005) contain the low and high
bytes of the address of the program to be executed as seen from the
6505 side of shared memory. To calculate the 6505 address, shift the
68000 address right one bit, then mask off the high order 9 bits.
INTERRUPTS
The Clear Interrupt Status command ($85) clears the interrupt line
from the 6505 to the 68000 using a mask found at $00C003. A one in
the mask byte clears the associated interrupt bit. Several interrupt
sources can cause the 6505 to assert the FDIR/ bit. The identity of
the interrupt source can be found at $00e081.
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7-Jul-81