LSI53C875 LSI Logic, LSI53C875 Datasheet - Page 127

• Manufacturer Part Number: LSI53C875
• Description: PCI to Ultra SCSI I/O Processor
• Manufacturer: LSI Logic

VUE1
WSR
Vendor Unique Enhancements Bit 1
This bit is used to disable the automatic byte count reload
during Block Move instructions in the command phase. If
this bit is cleared, the device reloads the Block Move byte
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.
Wide SCSI Receive
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
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.
SCSI Wide Residue (SWIDE)
register rather than
5-11
1
0