Chapter 4 Command Operation |
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Command List Structure | Page 4 - 19 |
Status Block OUT Index
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.
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
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.
User’s Guide | 21020285 D |
