2. PCI Interface
52
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
2.3.4
Terminations
This section describes the terminations supported by the PowerSpan II, how they are mapped from the
destination port to the PCI Target, and exception handling.
2.3.4.1
PCI Master Terminations
The PCI Master supports all four types of PCI terminations:
1.
Master-Abort: The PCI Master negates Px_FRAME# and then negates Px_IRDY# on the
following clock edge when no target responds with Px_DEVSEL# asserted on the fifth positive
edge of clock after Px_FRAME# is asserted. PowerSpan II sets R_MA in Px_CSR and records an
error condition in the event of a Master-Abort (see
2.
Target-Disconnect (with data): A termination is requested by the target
—
by asserting Px_STOP,
Px_DEVSEL# and Px_TRDY# — because it is unable to respond within the latency requirements
of the
PCI 2.2 Specification
or it requires a new address phase. Target-Disconnect means the
transaction is terminated after data is transferred. PowerSpan II negates Px_REQ# for at least two
clock cycles if it receives Px_STOP# from the PCI target.
3.
Target-Retry: Termination is requested
—
by asserting Px_STOP# and Px_DEVSEL# while
Px_TRDY# is high — by the target because it cannot currently process the transaction. Retry
means the transaction is terminated after the address phase without data transfer. PowerSpan II has
a Maximum Retry Counter (MAX_RETRY) in the
“PCI-1 Miscellaneous Control and Status
which is used to record an error condition if the number of retries exceed the
programmed amount (see
4.
Target-Abort: The target requests a termination of a transaction
—
by negating Px_DEVSEL# and
asserting Px_STOP# on the same clock edge
—
when it cannot respond to the transaction, or
during a fatal error. Although there may be a fatal error for the initiating application, the
transaction completes gracefully, ensuring normal PCI operation for other PCI resources.
PowerSpan II sets R_TA in Px_CSR and records an error condition in the event of a Target-abort
(see
2.3.4.2
Error Logging and Interrupts
The PowerSpan II PCI Master records errors under the following conditions:
•
Data Parity on reads
(
when the PERSP bit, in the
“PCI-1 Control and Status Register.” on
, is set)
•
Master-Abort
•
Target-Abort
•
Expiration of Maximum Retry Counter (when the MAX_RETRY field, in the
Miscellaneous Control and Status Register” on page 283
, is set.
and
“Interrupt Handling” on page 145
for a full description of error
logging support and associated interrupt mapping options.