2-56
Functional Description
transfers, in the chain byte holding register for synchronous transfers).
The stored byte is combined with the first byte of the following CHMOV
instruction.
CHMOV 0x5, 0x9 when Data-In
Moves five bytes from address 0x09 in the host memory to the SCSI bus.
The data in address 0x09 is married with the stored data (0x07) and
transferred to the SCSI bus.
2.2.18.1 Wide SCSI Send Bit
The WSS bit is set following a wide SCSI send operation (Data-Out for
initiator mode or Data-In for target mode) when the SCSI core is holding
a byte of chain data. The SCSI core holds the byte when 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
register for asynchronous transfers or in the chain
byte holding register for synchronous transfers, and the WSS flag is set.
The hardware uses the WSS bit to determine what behavior must occur
at the start of the next data send transfer. If the WSS bit is set at the
start of the next transfer, the first byte (the high-order byte) of the next
data send transfer is “married” with the byte of chain data. The two bytes
are sent out across the bus regardless of the type of Block Move
instruction (normal or chained). The WSS bit is automatically cleared
when the “married” word is sent. Performing either a SCSI receive
operation or any narrow transfer also clears the bit. In addition, SCRIPTS
and the microprocessor can clear the WSS bit as well as use it for error
detection and recovery purposes.
2.2.18.2 Wide SCSI Receive Bit
The WSR bit is set following a wide SCSI receive operation (Data-In for
initiator mode or Data-Out for target mode) when the SCSI core is
holding a byte of chain data. The SCSI core holds the byte when the
controller detects a partial transfer at the end of a Chained Block Move
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 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...