Seagate Ultra 160 ユーザーズマニュアル

Parallel SCSI Interface Product Manual, Rev. A                                        

   89

The INITIATOR DETECTED ERROR message is sent from an initiator to inform a target that an error has 
occurred that does not preclude the target from retrying the task. The source of the error may either be related 
to previous activities on the SCSI bus or may be internal to the initiator and unrelated to any previous SCSI bus 
activity. Although the integrity of the currently active pointers is not assured, a RESTORE POINTERS message 
or a physical disconnect followed by a reconnect shall cause the pointers to be restored to their defined prior 
state.

The LINKED COMMAND COMPLETE message is sent from a target to an initiator to indicate that a linkied 
command has completed and that status has been sent. The initiator shall then set the pointers to the initial 
state for the next linked command.

The MESSAGE PARITY ERROR message is sent from the initiator to the target to indicate that it received a 
message byte with a parity error (see Section 3.9.3.1). 

To indicate its intentions of sending this message, the initiator shall create an attention condition on the mes-
sage byte that has the parity error. This provides an interlock so that the target is able to determine which mes-
sage byte has the parity error. If the target receives this message under any other circumstance, it shall signal 
a catastrophic error condition by going to a BUS FREE phase without any further information transfer attempt 
(see Section 3.1.1).

If the target attempts a retry after receiving the MESSAGE PARITY ERROR message, the target shall return to 
the MESSAGE IN phase before switching to some other phase, the target shall resend the entire message that 
had the parity error.

The MESSAGE REJECT message is sent from either the initiator or target to indicate that the last message or 
message byte it received was inappropriate or has not been implemented. 

To indicate its intentions of sending this message, the initiator shall create an attention condition on the mes-
sage byte that is to be rejected. If the target receives this message under any other circumstance, it shall reject 
this message.

When a target sends this message, it shall change to MESSAGE IN phase and send this message prior to 
requesting additional message bytes from the initiator. This provides an interlock so that the initiator is able to 
determine which message byte is rejected.

After a target sends a MESSAGE REJECT message and if the attention condition is still set, then it shall return 
to the MESSAGE OUT phase. The subsequent MESSAGE OUT phase shall begin with the first byte of a mes-
sage.

The MODIFY DATA POINTER message (see Table 31) is sent from the target to the initiator and requests that 
the signed argument

 

be added to the value of the current data pointer using two's complement arithmetic. The 

data pointer is the data-out or data-in pointer being used by the command. The ENABLE MODIFY DATA 
POINTER (EMDP) bit in the Disconnect-reconnect mode page (see Seagate SCSI Command Reference Man-
ual, Part number 100293068) indicates whether or not the target is permitted to issue the MODIFY DATA 
POINTER message. The target shall only issue the MODIFY DATA POINTER message during a unidirectional 
command.