2-58
Functional Description
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. Since 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 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
register for 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 above, waiting to be married
with the first byte of the next Chained 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 (which will be the 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.
Содержание LSI53C1000
Страница 6: ...vi Preface...
Страница 16: ...xvi Contents...
Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
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Страница 318: ...6 44 Specifications This page intentionally left blank...
Страница 344: ...6 70 Specifications This page intentionally left blank...
Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Страница 352: ...6 78 Specifications...
Страница 360: ...A 8 Register Summary...
Страница 376: ...IX 12 Index...