21020285 D User’s Guide
Chapter 4 Command Operation
Page 4 - 6 The Base Status Block
The Base Status Block
The Status Block is another of the building blocks of the command structures
you will be using when issuing commands. Used in conjunction with the
Parameter Block, its purpose is to report the outcome of a command you issued.
The Status Block format is the same whether you have issued a Pass-through
command or a Board-control command. It appears the same whether the
command structure you used is a Single Command or a Command List,
however there is a difference in the number of Status Blocks you may receive
for each type of command structure.
Single Command structures return only one Status Block. The Single
Command structure will contain only the last Status Block—the Status Bloc k
with the CC (Command Complete) bit of the Flags byte set.
When you are using a Command List structure, multiple Status Blocks for any
one command are possible depending on the retry and Sense Byte selections
you have made (with the Unit Options or Extended Unit Options Board-contr ol
commands).
Status Block
Format
The Status Block Format you will see used for all returned status informat ion
is illustrated in the following figure:
Following is a brief description of each of the fields:
Command Identifier - This value will identify which Parameter Block has
completed.
Flags
This byte can be polled to determine whether, and in what condition, a
command completed. It has this format:
TMS Target Mode Status - This bit indicates that Status is being returned
from the Target Mode Response command.
0 ⇒ The status was not a result of a Target Mode Response command.
1 ⇒ The status is the result of a Target Mode Response command.
Address
Offset Byte Memory Offset
Offset + 0 Offset + 1 Offset + 2 Offset +3
00H Command Identifier
04H Error Flags
08H Status Information
0CH
Table 18: Base Status Block
BITS
76543210
CC ERR RTY DTT DTG CSB 0 TMS
Table 19: