Apple Lisa - Execute RWTS Command

Confidential
Lisa Hardware Reference Manual
When the 6505 generates an interrupt, the 68000 receives it as a
level 1 interrupt. The 68000 can discover the state of the floppy
disk interrupt request line by reading the location PB4 (also known
as FDIR) in the keyboard's 6522. If this bit is low, the floppy disk
controller has interrupted the 68000, so the 68000 can examine the
shared memory area to determine the results of the command. The
68000 should 'check the FDIR bit before accessing the shared memory
because the 6505 locks the 68000 out of the shared memory during a
disk transfer. If the 68000 tries to access the shared memory while
it is locked out, a Bus Timeout Error occurs.
THE EXECUTE RWTS COMMAND
The main part of the code in the
the Execute RWTS command ($81).
similar to those used by DOS 3.3
No. xxxxxxxxx) • As in DOS 3.3,
parameters to the RWTS routines.
disk controller ROM is executed by
The routines involved are very
(see the DOS 3.3 Manual, Apple Part
an I/O Block (lOB) is used to pass
FLOPPY DISK I/O COMMAND BLOCK
$00C003
$00C005
$00C007
$00C009
$OOCOOB
$OOCOOD
Command code
$00 Seek
$01 Read
$02 Write
$03 Reserved -
$04 Format
$05
Clamp
$06 Examine status
$07 Unclamp
Drive select
$00 Drive 2 (Bottom drive)
$80 Drive 1 (Top drive)
Side select
SOx Side 1
$ix Side 2
Sector number
Track number
Error code
$00 No error
(Top side)
(Bottom Side)
(0 to 22)
(0 to 44)
$40 Drive error
7-Jul-81
$OOCOll
$OOC015
$OOC019
$00C01D
$00C021
$OOC025
$OOC029
$OOC02D
$OOC031
Version number (2 bytes)
Volume number (2 bytes)
(Operating System Header)
File ID (2 bytes)
Data used (2 bytes)
Absolute page (2 bytes)
Relative page (2 bytes)
Forward link (2 bytes)
Backward link (2 bytes)
Previous drive number (drive accessed on last command)
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