Avago Technologies LSI53C1010 - Manual (Page 211)

Byte Recovery on Target Disconnect 9-13
9.3.2 Updating the SCRIPTS Program
After calculating the number of bytes in transition, you update the
SCRIPTS instruction so that the correct number of bytes are transferred
when the target reselects. This is done by updating the byte count and
address in the SCRIPTS program at wherever the current instruction was
at the time of disconnect. The SCRIPT is stored in the host's main
memory, so you can modify it at any time. You modify the binary version
of the instruction in host memory unless table indirect addressing is
used. If using Table Indirect Mode, you modify the byte count and
address in the data structure instead of the binary version of the
instruction.
9.3.3 Cleaning Up
Bytes that are already in transition must be processed. Depending on the
direction of transfer and how you write the code, any data left in the chip
must be flushed to memory (SCSI Receive only) or cleared and
discarded. The Flush DMA FIFO bit in the CTEST3 register flushes the
DMA FIFO data to memory. The Clear DMA FIFO bit in CTEST3
discards the data in the DMA FIFO. The Clear SCSI FIFO bit in STEST3
clears the data out of the Synchronous SCSI Receive FIFO and clears
data in any other intermediate registers.
In a normal disconnect situation, when a Phase Mismatch interrupt
occurs during a SCSI receive, no data should be left in the chip except
in the SWIDE register.
Note: The Wide SCSI Send and Wide SCSI Receive bits are
cleared by any nonwide send or receive action, such as
moving message bytes. Examine these bit values first
during byte recovery.
9.3.4 Example Byte Recovery Code
Byte recovery must be done when the SCRIPTS processor receives a
phase mismatch interrupt either during the Data In or Data Out phase.
Figure
9.7 is example code for moving data. Figures 9.8 and 9.9 are two
example functions which handle these situations.