Datasheet

Data Buffer Management

3-6 C141-C008

Table 3.1 Parameters for controlling reconnection timing

[Disconnect/Reconnect Parameter (Page code = 2)]

Bit

Byte

7 6 5 4 3 2 1 0

0 0 0 0 0 0 0 1 0

1 X‘0E’ (Page Length)

Buffer Full Ratio 2

Default Value: X‘00’

Variable Range: X‘00’ to X‘FF’

Buffer Empty Ratio 3

Default Value: X‘00’

Variable Range: X‘00’ to X‘FF’

(Other parameters)

a. Buffer full ratio

This parameter specifies the timing for the IDD to open the loop to perform

data transfer to the INIT in a 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 FC Interface is started.

If it is possible to transfer the amount of data specified in this parameter to

the INIT from the data buffer, Loop OPEN processing is executed and

transfer of data to the INIT begins. However, if the total amount of transfer

data specified in the command does not fill the capacity of the cache

segment, the IDD executes Loop OPEN processing and begins transferring

data to the INIT when it becomes possible to transfer the amount of data

blocks from the data buffer which is equivalent to the proportion of the total

volume of transfer data blocks specified in the command that is specified by

this parameter.

For example, if a read operation of 16 blocks with a logical data block length

of 512 bytes (8 Kbytes) is requested, when the value specified in this

parameter is 32, Loop OPEN processing is performed when it becomes

possible to transfer 2 blocks of data [16 x (32/256)], from the data buffer.