Altera PCI Compiler - Manual (Page 199)

Altera Corporation User Guide Version 11.1 3–125
October 2011
Functional Description
Abnormal Master Transaction Termination
An abnormal transaction termination is one in which the local side did
not explicitly request the termination of a transaction by asserting the
lm_lastn
signal. A master transaction can be terminated abnormally for
several reasons. This section describes the behavior of the pci_mt64 and
pci_mt32
functions during the following abnormal termination
conditions:
■ Latency timer expires
■ Target retry
■ Target disconnect without data
■ Target disconnect with data
■ Target abort
■ Master abort
Latency Timer Expires
The PCI specification requires that the master device end the transaction
as soon as possible after the latency timer expires and the gntn signal is
deasserted. The pci_mt64 and pci_mt32 functions adhere to this rule,
and when they end the transaction because the latency timer expired,
they assert lm_tsr[4] (tsr_lat_exp) until the beginning of the next
master transaction.
1 The PCI MegaCore functions allow the option of disabling the
latency timer for embedded applications. Refer to
“Disable
Master Latency Timer” on page 2–6 for more information.
Retry
The target issues a retry by asserting stopn and devseln during the first
data phase. When the pci_mt64 and pci_mt32 MegaCore functions
detect a retry condition (refer to
“Retry” on page 3–77 for details), they
end the cycle and assert lm_tsr[5] until the beginning of the next
transaction. This process informs the local-side device that it has ended
the transaction because the target issued a retry.
1 The PCI specification requires that the master retry the same
transaction with the same address at a later time. It is the
responsibility of the local-side application to ensure that this
requirement is met.