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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.

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Altera PCI Compiler Manual do Utilizador Página 160