7.7 Bus Conditions
(2) Response against ATTENTION condition (TARG)
The TARG must enter the MESSAGE OUT phase and respond to the ATTENTION condition under the following situations. After terminating the MESSAGE OUT phase and sending back a MESSAGE REJECT message, the TARG must reenter the MESSAGE OUT phase if the ATN signal is true.
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When the ATN signal becomes true in the COMMAND phase, the TARG must initiate the MESSAGE OUT phase immediately after the command (command descriptor block [CDB]) has completed the transfer of all or some bytes.
When the ATN signal becomes true in the DATA phase, the TARG must enter the MESSAGE OUT phase immediately after the DATA phase. The TARG can enter the MESSAGE OUT phase at any time. (For example, the data transfer need not be terminated at a logical data block boundary.) The INIT must continue REQ/ACK handshaking (DATA phase) until the bus phase changes.
When the ATN signal becomes true in the STATUS phase, the TARG must enter the MESSAGE OUT phase after the status byte transfer is completed.
When the ATN signal becomes true in the MESSAGE IN phase, the TARG must enter the MESSAGE OUT phase immediately after transferring the current message.
When the ATN signal becomes true in the SELECTION phase, the selected TARG must enter the MESSAGE OUT phase immediately after the SELECTION phase.
When the ATN signal becomes true in the RESELECTION phase, the TARG must enter the MESSAGE OUT phase after the IDENTIFY message transmission is completed.
