Reset Condition - Fujitsu MBA3073 SERIES Technical Manual

1.7.2

RESET condition

The RESET condition allows all SCSI devices to release immediately from the bus. RESET has
higher priority than any other phases and bus conditions. Any SCSI device can generate the
RESET condition anytime by keeping the RST signal true for Reset Hold Time or more. The state
of all bus signals except RST signals are undefined during the RESET condition.
All SCSI devices shall stop driving all bus signals (except for the RST signal) and release the bus
within Bus Clear Delay after the RST signal becomes true. After the RESET condition, the SCSI
bus always enters the BUS FREE phase. Figure 1.42 shows the RESET condition.
The following are the HDD operations when the RESET condition is detected.
1) Clears all commands including the currently executing commands and queued commands.
2) Releases the reserved disk state of the disk drive.
3) Initializes the operation mode to its initial status just after power-on if it has been set by the
message or command.
•
The current value of the parameter set by the MODE SELECT command is initialized to
the saved value previously established. If the value is not saved, it is initialized to the
default value.
•
The synchronous transfer parameters defined between the HDD and other SCSI device
are cleared. Any data transfer mode between all SCSI devices is initialized to the
asynchronous mode.
4) The UNIT ATTENTION condition is generated for all SCSI devices.
5) The sense data is no longer retained and is cleared.
6) All data read into the data buffer in advance by the read-ahead cache feature is invalidated.
Notes:
1. The HDD does not generate a RESET condition.
2. The HDD provides only "hard" RESET condition specified by the SCSI standard.
3. Reset Hold Time is specified to guarantee that any SCSI device can recognize the
occurrence the RESET condition. On the HDD, even if the pulse width is less than Reset
Hold Time, the RESET condition is effective.
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