LSI LSI53C895A, Technical Manual

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SCSI Registers 4-79
•
Data Overflow – writing too many bytes to the SCSI
FIFO, or the synchronous offset causes overwriting
the SCSI FIFO.
•
Offset Underflow – the LSI53C895A is operating in
target mode and a SACK/ pulse is received when the
outstanding offset is zero.
•
Offset Overflow – the other SCSI device sends a
SREQ/ or SACK/ pulse with data which exceeds the
maximum synchronous offset defined by the
SCSI
Transfer (SXFER) register.
•
A phase change occurs with an outstanding
synchronous offset when the LSI53C895A is
operating as an initiator.
•
Residual data in the synchronous data FIFO – a
transfer other than synchronous data receive is
started with data left in the synchronous data FIFO.
UDC Unexpected Disconnect 2
This bit is set when the LSI53C895A is operating in the
initiator mode and the target device unexpectedly
disconnects from the SCSI bus. This bit is only valid
when the LSI53C895A operates in the initiator mode.
When the LSI53C895A operates in low level mode, any
disconnect causes an interrupt, even a valid SCSI
disconnect. This bit is also set if a selection time-out
occurs (it may occur before, at the same time, or stacked
after the STO interrupt, since this is not considered an
expected disconnect).
RST SCSI RST/ Received 1
This bit is set when the LSI53C895A detects an active
SRST/ signal, whether the reset is generated external to
the chip or caused by the Assert RST bit in the
SCSI
Control One (SCNTL1) register. This SCSI reset
detection logic is edge-sensitive, so that multiple
interrupts are not generated for a single assertion of the
SRST/ signal.
PAR Parity Error 0
This bit is set when the LSI53C895A detects a parity
error while receiving SCSI data. The Enable Parity
Checking bit (bit 3 in the
SCSI Control Zero (SCNTL0)