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User’s Guide 21020285 D
Chapter 4 Command Operation
Command List Structure Page 4 - 19
Status Block OUT Index
The Status Block OUT Index advances when the Host reads a Status Block
from the array to indicate that a Status Block has been read. This value is never
changed by the adapter.
Number of Parameter Blocks
This value indicates the maximum number of Parameter Blocks that you can
have active in the list. You should pick a number that is adequate for the number
of commands that you will issue. Since the Status Block array follows the
Parameter Block array, you cannot increase this number once execution begins.
The maximum space available to use for Parameter Blocks is 65536 bytes.
Since each Parameter Block is 28 bytes long, the maximum number of
Parameter Blocks you can have is 2340.
0 and 1 are not valid values to use in this field.
Number of Status Blocks
Note
Multiple Status Blocks
generated from retries or
extended Sense data
must be factored into the
value you select for this
field. Retries and
additional Sense data
options are enabled
through use of the Unit
Options or Extended
Unit Options commands.
This value indicates the number of Status Blocks available to be written by the
adapter in the Command List. Maximum space available for Status Blocks is
65536 bytes. Since each Status Block is 16 bytes long, the maximum number
of Status Blocks you can have is 4096.
0 and 1 are not valid values to use in this field.
Parameter Block Space
You may have up to 2340 Parameter Blocks in the Command List Structure
simultaneously. The Parameter Block area is treated as an independent circular
list. First you place a Parameter Block into this area, then the adapter reads it
to execute.
Status Block Space
You may have up to 4096 Status Blocks in this area simultaneously. The Status
Block area is treated as a circular list separate from the Parameter Block area.
When the adapter places a Status Block into this area, it is available to be read
in from the Host side.
It is possible to generate multiple Command List Status Blocks from one Pass-
through command if retries are enabled and more than eight bytes of Sense data
are selected. Retries and Sense data are enabled with the Unit Options or
Extended Unit Options commands.