Avago Technologies LSI53C1010R User Manual
Page 87
SCSI Functional Description
2-57
Version 2.2
Copyright © 2000–2003 by LSI Logic Corporation. All rights reserved.
transfer. Performing either a SCSI send operation or any narrow transfer
also clears the bit. In addition, SCRIPTS and the microprocessor can clear
the WSR bit as well as use it for error detection and recovery purposes.
2.2.18.3 SWIDE Register
For wide asynchronous receive data transfers, the
register holds the high-order byte of a
partial SCSI transfer which has not yet been transferred to memory. This
stored data may be a residue byte (and therefore ignored) or it may be
valid data that is transferred to memory at the beginning of the next data
receive Block Move instruction.
2.2.18.4 SODL Register
For wide asynchronous send data transfers, the low-order byte of the
register holds the low-order byte of a
partial memory transfer which has not yet been transferred across the
SCSI bus. This stored data is usually “married” with the first byte of the
next data send transfer, and both bytes are sent across the SCSI bus at
the start of the next data send Block Move instruction.
2.2.18.5 Chained Block Move SCRIPTS Instruction
A Chained Block Move SCRIPTS instruction primarily transfers
consecutive data send or data receive blocks. Using the Chained Block
Move instruction facilitates partial receive transfers and allows correct
partial send behavior without additional opcode overhead. The behavior
of the Chained Block Move instruction varies slightly for sending and
receiving data.
For receive data (Data-In for the initiator or Data-Out for the target), a
Chained Block Move instruction indicates that if a partial transfer occurred
at the end of the instruction the WSR flag is set. The high order byte of
the last SCSI transfer is stored in the
register rather than transferred to memory. The stored byte should be the
first byte transferred to memory at the start of the Chained Block Move or
regular Block Move data stream. Because the byte count always
represents data transfers to/from memory (as opposed to/from the SCSI
bus), the stored byte transferred out is one of the bytes in the count. If the
WSR bit is cleared when a receive data Chained Block Move instruction is