Status WordThe status word is a 16-bit structured field used to hold flags indicating how the com-mand for the associated control block is completed.F E D C B A 9 8 7 6 5 4 3 2 1 0E M I S A I C D S Q D DC E N N S N H O C F U OA I S A T NFields that are empty are reserved and will be set to zero.Flag Name and FunctionDON Command Done - No ErrorThe Command Done flag (bit 0) indicates whether the control block completed suc-cessfully.If this bit is one, the control block completed without error.If this bit is zero, the other flags in this word as well as the host adapter and targetstatus bytes should be analyzed to determine the completion status of the controlblock.When this flag is zero, the status block is stored unconditionally by the host adapterand an interrupt is generated, regardless of the settings of the Disable Interruptand Disable Status Block flags (Flag Word 1, bits 7 and 14, respectively).DU Data UnderrunThe Data Underrun flag (bit 1) indicates whether the amount of data transferredwas less than the amount specified by the data length field in the control block.If this bit is one, a data underrun occurred. the residual byte count and residualbuffer address fields are valid. If the Suppress Error on Underrun flag (Flag Word1, bit 10) was set to one, then the Command Done flag will also be set to one,indicating that the underrun condition was not considered an error. If the SuppressError on Underrun flag was set to zero, then the Command Done flag will be set tozero and the Major Error/Exception flag will be set to one.If this bit is zero, no underrun condition was detected.QF Host Adapter Queue FullThe Queue Full flag (bit 3) indicates that the host adapter was not able to acceptthe control block.If this bit is set to one, the host adapter has rejected the control block because itsinternal storage area is full. No action is taken on the control block. The host shouldreissue the control block after an outstanding control block completes or after anappropriate time delay.adaptec AHA-1740A/1742A/17446-14
