LSI LSI53C896, Technical Manual

Page: 79 / 370

SCSI Functional Description 2-53
Figure 2.9 Block Move and Chained Block Move Instructions
CHMOV 5, 3 when Data_Out
Moves five bytes from address 0x03 in the host memory to the SCSI bus.
Bytes 0x03, 0x04, 0x05, and 0x06 are moved and byte 0x07 remains in
the low-order byte of the
SCSI Output Data Latch (SODL) register and
is combined with the first byte of the following MOVE instruction.
Move 5, 9 when Data_Out
Moves five bytes from address 0x09 in the host memory to the SCSI bus.
2.2.18.1 Wide SCSI Send Bit
The WSS bit is set whenever the SCSI controller is sending data
(Data-Out for the initiator or Data-In for the 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
0x03 0x02 0x01 0x00
0x07 0x06 0x05 0x04
0x0B 0x0A 0x09 0x08
0x0F 0x0E 0x0D 0x0C
0x13 0x12 0x11 0x10
0x04 0x03
0x06 0x05
0x09 0x07
0x0B 0x0A
0x0D 0x0C
32 Bits 16 Bits
Host Memory SCSI Bus
00
04
08
0C
10
*