Register: 0x0A

SCSI Selector ID (SSID)

Read Only

7

6

 

 

4

3

 

 

 

0

VAL

 

 

R

 

 

 

ENID

 

0

x

 

x

x

0

0

 

0

0

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

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

 

 

 

 

 

 

 

 

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.

4-38Registers

Page 130
Image 130
LSI 53C875A technical manual Register 0x0A, Register 0x0B, Val, Enid