CMP

Function Complete

6

 

Indicates full arbitration and selection sequence is

 

 

completed.

 

SEL

Selected

5

 

Indicates the LSI53C875A is selected by a SCSI initiator

 

device. Set the Enable Response to Selection bit in the

 

SCSI Chip ID (SCID) register for this to occur.

 

RSL

Reselected

4

 

Indicates the LSI53C875A is reselected by a SCSI target

 

device. Set the Enable Response to Reselection bit in the

 

SCSI Chip ID (SCID) register for this to occur.

 

SGE

SCSI Gross Error

3

 

The following conditions are considered SCSI Gross

 

 

Errors:

 

 

Data underflow – reading the SCSI FIFO when no

 

 

data is present.

 

 

Data overflow – writing to the SCSI FIFO while it is

 

 

full.

 

 

Offset underflow – receiving a SACK/ pulse in target

 

mode before the corresponding SREQ/ is sent.

 

 

Offset overflow – receiving an SREQ/ pulse in the

 

 

initiator mode, and exceeding the maximum offset

 

 

(defined by the MO[3:0] bits in the SCSI Transfer

 

 

(SXFER) register).

 

 

A phase change in the initiator mode, with an

 

 

outstanding SREQ/SACK/ offset.

 

 

Residual data in SCSI FIFO – starting a transfer other

 

than synchronous data receive with data left in the

 

 

SCSI synchronous receive FIFO.

 

UDC

Unexpected Disconnect

2

 

This condition only occurs in the initiator mode. It

 

 

happens when the target to which the LSI53C875A is

 

connected disconnects from the SCSI bus unexpectedly. See the SCSI Disconnect Unexpected bit in the SCSI Control Two (SCNTL2) register for more information on expected versus unexpected disconnects. Any disconnect in low level mode causes this condition.

4-74Registers

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LSI 53C875A technical manual Cmp, Rsl, Sge, Udc