SCSI Registers
4-29
count if the first byte received is one of the standard
group codes. If this bit is set, the device does not reload
the Block Move byte count, regardless of the group code.
WSR
Wide SCSI Receive
0
When read, this bit returns the value of the Wide SCSI
Receive (WSR) flag. Setting this bit clears the WSR flag.
This clearing function is self-clearing.
The WSR flag indicates that the SCSI core received data
from the SCSI bus, detected a possible partial transfer at
the end of a chained or nonchained block move
command, and temporarily stored the high-order byte in
the
register rather than
passing the byte out the DMA channel. The hardware
uses the WSR status flag to determine what behavior
must occur at the start of the next data receive transfer.
When the flag is set, the stored data in SWIDE may be
“residue” data, valid data for a subsequent data transfer,
or overrun data. The byte is read as normal data by
starting a data receive transfer.
Performing a SCSI send operation clears this bit. Also,
performing any nonwide transfer clears this bit.
Register: 0x03
SCSI Control Three (SCNTL3)
Read/Write
USE
Ultra SCSI Enable
7
Setting this bit enables Ultra SCSI or Ultra2 SCSI
synchronous transfers. The default value of this bit is 0.
This bit should remain cleared if the LSI53C895A is not
operating in Ultra SCSI mode or faster.
When this bit is set, the signal filtering period for SREQ/
and SACK/ automatically changes to 8 ns for Ultra2 SCSI
or 15 ns for Ultra SCSI, regardless of the value of the
Extend REQ/ACK Filtering bit in the
register.
7
6
4
3
2
0
USE
SCF[2:0]
EWS
CCF[2:0]
0
0
0
0
0
0
0
0
Содержание LSI53C895A
Страница 1: ...S14028 B LSI53C895A PCI to Ultra2 SCSI Controller TECHNICAL MANUAL A p r i l 2 0 0 1 Version 2 2...
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