MPC8540 datasheet(922/1302 Pages) FREESCALE

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MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

16-100

Freescale Semiconductor

PCI/PCI-X Bus Interface

The POR reset values for the affected configuration bits are described in Table 16-67.

16.5.1.1 Host Mode

When the device powers up in host mode, all inbound configuration accesses are ignored (and thus

master aborted). The ACL bit is a don’t care. The device powers up with the ability to master

transactions on the PCI bus, however in order to acknowledge memory transactions, the memory

space bit must be set.

16.5.1.2 Agent Mode

When the device powers up in agent mode, it acknowledges inbound configuration accesses.

However the device cannot master transactions or acknowledge inbound memory accesses on the

PCI bus until the appropriate configuration bits (bus master and memory space, respectively) have

been set.

16.5.1.3 Agent Configuration Lock Mode

Agent configuration lock mode is similar to agent mode with the added restriction that when the

device powers up in agent configuration lock mode, it retries all inbound configuration accesses

until the ACL bit is cleared. As in agent mode, the device in agent configuration lock mode cannot

master transactions or acknowledge inbound memory accesses on the PCI bus until the appropriate

configuration bits (bus master and memory space, respectively) have been set.

16.5.2 Nonposted Writes in PCI-X

The PCI-X block may pipeline I/O write and configuration write accesses to a target that signals

a split response. To fully serialize these non-posted writes, the processor should follow each write

transaction with a read of the same target, followed by proper barrier instructions to guarantee

completion of the read before continuing with a subsequent write. This method guarantees

completion of the write and serialization of a series of writes.

Table 16-67. Power-On Reset Values for Affected Configuration Bits

Mode

Configuration Bit

Bus Master

Memory Space

ACL

PAH

Host

Agent

0001

Agent configuration

lock

0011

MPC8540 Datasheet(PDF) 922 Page - Freescale Semiconductor, Inc