LSI53CF92A LSI, LSI53CF92A Datasheet - Page 23

• Manufacturer Part Number: LSI53CF92A
• Manufacturer: LSI

Specifications of LSI53CF92A

• Lead Free Status / RoHS Status: Not Compliant

2.2 Bus-Initiated Sequences
The end of a SCSI transaction is similar for an FSC initiator except that it
receives two bytes into its FIFO. The initiator prevents the target from
disconnecting by holding ACK/ asserted on the bus while the
microprocessor examines the status and message bytes. If both bytes are
acceptable, the Message Accepted command instructs the FSC to release
ACK/, which allows the target to disconnect and causes the initiator to
interrupt its host and report the disconnect. If the status and message
bytes are not acceptable, the host could first issue the Set ATN (Attention)
command before issuing the Message Accepted command. This instructs
the FSC to assert ATN/ before releasing ACK/, which should cause the
target to request Message Out phase rather than disconnect.
Selection or reselection sequences occur in the disconnected state when
the FSC is selected or reselected by another initiator or target, if the
Enable Selection or Reselection command has previously been received
by the FSC.
In addition to responding to bus-initiated events, the FSC may initiate a
bus event by using one of several selection or reselection commands. If
one of these commands starts executing, the Enable Selection or
Reselection command is cleared after another device has been selected,
preventing the FSC from responding to a Select or Reselect command.
Normally the microprocessor has 250 ms (ANSI recommended selection
time-out period) after the chip disconnects from the bus to re-enable bus-
initiated events. If the time-out period is exceeded, an initiator or target
which is attempting to connect to the FSC may time-out and abort.
If, on the other hand, the bus-initiated event occurs before the command
starts executing, the FIFO and command register is cleared and any
further writes by the microprocessor are ignored until the Interrupt register
is read. Because a selection or reselection command requires placing
something in the FIFO, these bytes are lost, as is any command written
to the
or reselection command has to examine the bits in the
Bus-Initiated Sequences
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Selection
Reselection
SCSI bus reset
Command
register. The interrupt handler that services a selection
Interrupt
register
2-3