3. Processor Bus Interface
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PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
•
Data Valid (PB_DVAL_): This signal is asserted by the PB slave to indicate the successful transfer
of an 8-byte quantity within an extended transfer of 16 or 24 bytes. PB_TA_ is asserted together
with PB_DVAL_ on the transfer of the last 8-byte quantity.
•
Transfer Error Acknowledge (PB_TEA_): This signal indicates an unrecoverable error and causes
the external master to immediately terminate the data tenure.
3.3.3.2
Assertion of PB_TEA_
PowerSpan II asserts PB_TEA_ when a particular slave image cannot handle transactions involving
more than 4 bytes. This applies to the following:
•
)
•
accesses to general purpose slave image configured for PCI I/O space
•
access to registers designed to generate PCI Configuration or IACK commands (see
“Configuration and IACK Cycle Generation” on page 246
PowerSpan II also asserts PB_TEA_ if a read from PCI generates a Master-Abort or Target-Abort.
The assertion PB_TEA_ is enabled or disabled with the TEA Enable (TEA_EN) bit in the
Bus Miscellaneous Control and Status Register” on page 304
3.3.3.3
Errors
The PowerSpan II PB Slave detects the following error conditions:
•
address parity
•
data parity on writes
•
illegal accesses
and
“Interrupt Handling” on page 145
for a full description of error
logging support and associated interrupt mapping options.
The PB Slave does not assert a data termination signal earlier than the
address retry window
.
In a development environment, the TEA_EN bit is set to allow the assertion of PB_TEA_ to
support the debug of software. In a production environment, customers may find it useful to
disable the assertion of PB_TEA_.