combined with the first byte from the subsequent transfer so that a wide transfer is completed.

SLPMD

SLPAR Mode

5

 

If this bit is cleared, the SCSI Longitudinal Parity (SLPAR)

 

register functions as a byte-wide longitudinal parity

 

 

register. If this bit is set, the SLPAR functions as a

 

 

word-wide longitudinal parity function. The high or low

 

 

byte of the SLPAR word is accessible through the SLPAR

 

register. Which byte is accessible is controlled by the

 

 

SLPHBEN bit.

 

SLPHBEN

SLPAR High Byte Enable

4

 

If this bit is cleared, the low byte of the SLPAR word is

 

 

accessible through the SCSI Longitudinal Parity (SLPAR)

 

register. If this bit is set, the high byte of the SLPAR word

 

is present in the SLPAR register.

 

WSS

Wide SCSI Send

3

 

When read, this bit returns the value of the Wide SCSI

 

 

Send (WSS) flag. Asserting this bit clears the WSS flag.

 

This clearing function is self-clearing.

 

 

When the WSS flag is high following a wide SCSI send

 

operation, the SCSI core is holding a byte of “chain” data

 

in the SCSI Output Data Latch (SODL) register. This data

 

becomes the first low-order byte sent when married with

 

a high-order byte during a subsequent data send transfer.

 

Performing a SCSI receive operation clears this bit. Also,

 

performing any nonwide transfer clears this bit.

 

VUE0

Vendor Unique Enhancements, Bit 0

2

 

This bit is a read only value indicating whether the group

 

code field in the SCSI instruction is standard or vendor

 

 

unique. If cleared, the bit indicates standard group codes;

 

if set, the bit indicates vendor unique group codes. The

 

value in this bit is reloaded at the beginning of all

 

 

asynchronous target receives.

 

VUE1Vendor Unique Enhancement, Bit 11

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

SCSI Registers

4-27

Page 119
Image 119
LSI 53C875A technical manual Slpmd, Slphben, Wss, VUE0