QSEL

SCLK Quadrupler Select

2

 

This bit, when set, selects the output of the internal clock

 

quadrupler for use as the internal SCSI clock. When

 

cleared, this bit selects the clock presented on SCLK for

 

use as the internal SCSI clock.

 

R

Reserved

[1:0]

Register: 0x4E

SCSI Test Two (STEST2)

Read/Write

7

6

5

4

 

3

2

1

0

SCE

ROF

 

R

SLB

 

SZM

AWS

EXT

LOW

0

0

 

0

0

 

0

0

0

0

SCE

 

SCSI Control Enable

 

 

 

7

Setting this bit allows assertion of all SCSI control and data lines through the SCSI Output Control Latch (SOCL) and SCSI Output Data Latch (SODL) registers regardless of whether the LSI53C875A is configured as a target or initiator.

Note:

Do not set this bit during normal operation, since it could

 

 

cause contention on the SCSI bus. It is included for

 

 

diagnostic purposes only.

 

ROF

Reset SCSI Offset

6

 

Setting this bit clears any outstanding synchronous

 

 

SREQ/SACK offset. Set this bit if a SCSI gross error

 

 

condition occurs and to clear the offset when a

 

 

synchronous transfer does not complete successfully.

 

 

The bit automatically clears itself after resetting the

 

 

synchronous offset.

 

R

Reserved

5

 

This bit must be cleared.

 

SLB

SCSI Loopback Mode

4

Setting this bit allows the LSI53C875A to perform SCSI loopback diagnostics. That is, it enables the SCSI core to simultaneously perform as both the initiator and the target.

SCSI Registers

4-89

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LSI 53C875A technical manual Register 0x4E, Qsel, Sce, Rof, Slb