Avago Technologies LSI53C1010R User Manual

Page 88

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Functional Description

Version 2.2

executed, the data transfer occurs similar to that of the regular Block Move
instruction. It is recommended that all Block Move instructions be
Chained Block Moves.

For send data (Data-Out for the initiator or Data-In for the target), a Chained
Block Move instruction indicates that if a partial transfer terminates, the
Chained Block Move the WSS flag is set. The low-order byte should be
stored in the lower byte of the

SCSI Output Data Latch (SODL)

asynchronous transfers or in the chain byte holding register for
synchronous transfers and not sent across the SCSI bus. Without the
Chained Block Move instruction, the last low-order byte would be sent
across the SCSI bus. The starting byte count represents data bytes
transferred from memory but not to the SCSI bus when a partial transfer
exists. For example, if the instruction is an initiator Chained Block Move
Data Out of five bytes (and WSS is not previously set), five bytes are
transferred out of memory to the SCSI controller. Four bytes are transferred
from the SCSI controller across the SCSI bus and one byte is temporarily
stored as described, waiting to be “married” with the first byte of the next
Block Move instruction. If the WSS bit is set at the start of a data send
command, the first byte of the transfer is assumed to be the high-order byte
and is “married” with the stored byte (low-order byte) before the two bytes
are sent across the SCSI bus. It is recommended that all Block Move
instructions be Chained Block Moves.