Apple Lisa - Floppy Disk Controller; Disk Controller Commands

ConfidentiaJ
Lisa Hardware Reference Manual
THE FLOPPY DISK CONTROLLER
The built-in floppy disk controller consists of a 6505 based
microcomputer and a
disk interface similar to that of the Apple II.
The 6505 has 1 KByte of RAM and 4 KBytes of ROM. The RAM is shared
with the 68000 address space. The 68000 and 6505 communicate data
and commands through this shared memory. Use the MOVEP instruction
to convert 16 bit 68000 data to the 8 bit 6505 format. When data
moves from the 6505 to the 68000, the shared memory appears in the
low byte of each word read by the 68000.
At power on, the 6505 sets the disk control lines to a safe state,
does a checksum on the ROM, tests the RAM, clears some of the RAM,
and leaves the results of the ROM and RAM tests in the location
$00C003. The 6505 then interrupts the 68000 and waits for a command.
DISK CONTROLLER COMMANDS
The command block consists of 20 bytes in the low 20 words of the
6505 address space. 17 of these bytes are used to pass parameters
to the Read/Write/Track/Sector (RWTS) routine. The other 3 bytes
are used for communication between the 68000 and the 6505. The
command byte appears. at the 68000 address $00ca01, and at the 6505
address $0000.
The disk controller reads the command byte until a valid command
appears, or until an interrupt arrives from the disk drives. The
disk drives generate an interrupt when the eject button is pushed
and when the disk is in place. When a valid command appears, the
controller reads the command, clears the command byte, executes the
command, and interrupts the 68000 if necessary. The controller then
waits for the next command.
FLOPPY DISK CONTROLLER COMMANDS
(68000 writes to $OOCOOO)
$81 Execute RWTS USing $00C003 - $00C031 as parameters
$84 JSR to routine pointed to by $OOC003 and $OOC005
$85 . Clear Interrupt Status
$86 Set Interrupt Mask
$87 Clear Interrupt Mask
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7-Jul-81