Fujitsu MAX3073NC - SCSI,80, Dell DC961,Hard Drive Scsi Logical Interface Specifications page 195

Note:
If transfer of this page descriptor is required by the MODE SENSE or MODE SENSE EXTENDED
command, the IDD reports X '0E' as the page length (byte 1). However, if either X '0E' or X '0A' is
specified for the page length in the MODE SELECT command, the IDD regards it as if the correct page
length was specified. The X '0A' page length, is provided in consideration of compatibility with previous
models, but it is recommended that the page length X '0E' be used by the INIT to support expansions in the
specifications in the future.
See Section 2.1, "Data Buffer" concerning specification methods for the "Buffer Full Ratio" and "Buffer Empty
Ratio" parameters in this page descriptor and details of data buffer operation.
a. Buffer full ratio
This parameter specifies the timing for the IDD to start reconnection processing in order to transfer
data to the INIT by the READ or READ EXTENDED command.
The value specified in this parameter (n) shows the amount of data read to the IDD's data buffer from
the disk media as a proportion [n/256] of the total capacity of the data buffer until reconnection
processing with the SCSI bus is started. (Note)
If it is possible to transfer the amount of data specified in this parameter to the INIT from the data buffer,
reconnection processing is executed and transfer of data to the INIT begins.
The default value for this parameter is X'00'. The host can also specify X'00' for this parameter. If
X'00'is specified, the IDD assigns an appropriate value for this parameter that is determined by IDD.
b. Buffer empty ratio
This parameter specifies the timing for the IDD to start reconnection when it is requested by the INIT to
transfer data in the WRITE, WRITE EXTENDED or WRITE AND VERIFY command.
The value specified in this parameter (n) indicates the size of the empty area in the IDD's data buffer
as a proportion of the total data buffer capacity of the IDD [n/256]. (Note)
While the IDD is writing data to the disk media, it is using the data pre-fetched to the data buffer in
order, and when the empty space in the data buffer reaches the amount specified in this parameter, it
executes reconnection processing, requesting transfer of the succeeding data.
If the total number of bytes in the transferred data block count specified in the command is less than
the capacity of the buffer segment, all the data are pre-fetched in a batch, so the specification in this
parameter is not applied.
The default value for this parameter is X'00'. The host can also specify X'00' for this parameter. If
X'00'is specified, the IDD assigns an appropriate value for this parameter that is determined by IDD.
C141-C010
4.1 Mode Parameters
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