Commodore Amiga A500 Technical Reference Manual page 170

I/O addresses unique to
board
SCSI Controller
40/42
15/14/13/12 15/14/13/12
*Signals unique to Amiga Hard Disk/SCSI Controller.
SSEL
HCBP.CCBP
48H
50H
52H
60H
62H
64H
68H
WRITE
Interrupt enable
*SSEL
MRESET
*HCBP bit
not defined
not defined
not defined
not defined
Used to select SCSI controller or to ST605
controller. High = SCSI, low = ST506.
Host command block pointer and Controller
command block pointer. Used to handshake
address of Command block pointer to ST506
Base address register
PROCC-lnterrupt ST506 controller to process
command. Write only. Data value written from
host is XXXI hex.
WRCBP/INTACK - Multiplexed signal. WRCBP
strobes the command block pointer register. IN-
TACK clear INTP at end of command.
CS - Chip select for the WD33C93 SCSI chip.
Used to write to the internal address register and
read from the internal status register.
CS - Chip select for the WD33C93 SCSI chip.
Used to write and read remaining Control regis
ters in the WD33C93.
SCSI PCSS - Used to initialize the 8727(DMA) in
SCSI mode. Refer to section 5.0 for 8727 com
mands
SCSI PCSD - Used to pas data to and from the
8727 in SCSI mode. Refer to section 5.0 for
transfer procedures.
167
READ
Interrupt enable
DON'T CARE
MUST BE ZERO
*CCBP bit
INT2 PENDING
ZERO
ZERO
INT FOLLOW