Datasheet

3.1 Data Buffer
C141-C008 3-3
5) If the number of blocks specified in the command to be transferred is
larger than the capacity of a cache segment and if the data transfer rate of
the INIT is lower than the data transfer rate of the disk drive, the empty
space in the data buffer disappears from step 3) and the IDD may soon
not be able to read data from the disk media (data overrun). In this case,
the IDD relocates the block that caused the data overrun after waiting
one disk revolution, and continues the reading process.
6) When transfer of all the specified data is completed, the IDD reports the
status and terminates the command.
In order to avoid frequent repetition of the Loop CLOSE/OPEN
processing after data frame transfer starts on the FC interface, and
avoid the occurrence of data overruns, it is necessary to set the
buffer full ratio (see Section 3.1.2) of the MODE SELECT
parameter so the difference in the data transfer rates between the
INIT (FC interface) and the disk drive is maintained in a good
balance.
Figure 3.2 shows an example of the data buffer operating state during a read
operation. Details are explained in Section 3.1.2.
Figure 3.2 Example of data buffer operation during read