LSI 53C875A - Manual (Page 67)

SCSI Functional Description 2-45
Figure 2.7 Block Move and Chained Block Move Instructions
2.2.17.1 Wide SCSI Send Bit
The WSS bit is set whenever the SCSI controller is sending data
(Data-Out for initiator or Data-In for target) and the controller detects a
partial transfer at the end of a chained Block Move SCRIPTS instruction
(this flag is not set if a normal Block Move instruction is used). Under this
condition, the SCSI controller does not send the low-order byte of the last
partial memory transfer across the SCSI bus. Instead, the low-order byte
is temporarily stored in the lower byte of the
SCSI Output Data Latch
(SODL) register and the WSS flag is set. The hardware uses the WSS
flag to determine what behavior must occur at the start of the next data
send transfer. When the WSS flag is set at the start of the next transfer,
the first byte (the high-order byte) of the next data send transfer is
“married” with the stored low-order byte in the SODL register; and the
0x02 0x01 0x00
0x0B 0x0A 0x09 0x08
0x0F 0x0E 0x0D 0x0C
0x13 0x12 0x11 0x10
0x09
0x0B 0x0A
0x0D 0x0C
0x07 0x06 0x05 0x04
0x04 0x03
0x06 0x05
0x07
Host Memory SCSI Bus
32 Bits 16 Bits
0x03