LSI 53C875A - Manual (Page 130)

4-38 Registers
Register: 0x0A
SCSI Selector ID (SSID)
Read Only
VAL SCSI Valid 7
If VAL is asserted, then the two SCSI IDs are detected
on the bus during a bus-initiated selection or reselection,
and the encoded destination SCSI ID bits below are valid.
If VAL is deasserted, only one ID is present and the
contents of the encoded destination ID are meaningless.
R Reserved [6:4]
ENID Encoded Destination SCSI ID [3:0]
Reading the SSID register immediately after the
LSI53C875A is selected or reselected returns the
binary-encoded SCSI ID of the device that performed the
operation. These bits are invalid for targets that are
selected under the single initiator option of the SCSI-1
specification. This condition is detected by examining the
VAL bit above.
Register: 0x0B
SCSI Bus Control Lines (SBCL)
Read Only
This register returns the SCSI control line status. A bit is set when the
corresponding SCSI control line is asserted. These bits are not latched;
they are a true representation of what is on the SCSI bus at the time the
register is read. The resulting read data is synchronized before being
presented to the PCI bus to prevent parity errors from being passed to
the system. This register is used for diagnostic testing or operation in low
level mode.
7 6 4 3 0
VAL R ENID
0 x x x 0 0 0 0
7 6 5 4 3 2 1 0
REQ ACK BSY SEL ATN MSG C_D I_O
x x x x x x x x