Altera PCI Compiler - Manual (Page 160)

3–86 User Guide Version 11.1 Altera Corporation
PCI Compiler October 2011
Target Mode Operation
Target Abort
Target abort refers to an abnormal termination because either the local
logic detected a fatal error, or the target will never be able to complete the
request. An abnormal termination may cause a fatal error for the
application that originally requested the transaction. A target abort
allows the transaction to complete gracefully, thus preserving normal
operation for other agents.
A target device issues an abort by deasserting devseln and trdyn and
asserting stopn. A target device must set the tabort_sig bit in the PCI
status register whenever it issues a target abort. Refer to
“Status Register”
on page 3–33 for more details. Figure 3–30 shows the PCI MegaCore
function issuing an abort during a burst write cycle. It applies to all PCI
MegaCore functions, excluding the 64-bit extension signals as noted for
pci_mt32
and pci_t32.
1 The PCI Local Bus Specification, Revision 3.0 requires that a target
device issues an abort if the target device shares bytes in the
same DWORD with another device, and the byte enable
combination received byte requests outside its address range.
This condition most commonly occurs during I/O transactions.
The local-side device must ensure that this requirement is met,
and if it receives this type of transaction, it must assert
lt_abortn
to request a target abort termination.