PLX Technology PEX 8311RDK, Справочник по аппаратуре

Страница: 21 / 66

PEX 8311RDK Hardware Reference Manual, Version 0.90
© 2005 PLX Technology, Inc. All rights reserved.
13
3.7 Power Management Signaling
Local devices assert the PMEIN# pin to signal a Power Management event. The PEX 8311 converts the
PMEIN# signal to PCI Express Power Management Event (PME) messages. There are no internal events
that cause a PME message to be sent upstream.
When the PME message is sent to the host, the PWRMNGCSR register PME Status bit is set and a
100-ms timer is started. If the status bit is not cleared within 100 ms, another PME message is sent.
When the upstream device is powering down the downstream devices, it first places all devices into the
D3
hot
state. It then sends a PCI Express PME_Turn_Off message. After the PEX 8311 receives this
message, it stops sending PME messages upstream. The PEX 8311 then sends a PME_TO_Ack
message to the upstream device and places its link into the L2/L3 Ready state. The downstream device is
now ready to be powered down. If the upstream device changes the PEX 8311 power state back to D0,
PME messages are re-enabled. The PCI Express PME_Turn_Off message terminates at the PEX 8311,
and is not communicated to the PCI devices. The PEX 8311 does not issue a PM_PME message on
behalf of a downstream PCI device while its upstream link is in the L2/L3 non-communicating state.
To avoid loss of PME# assertions in the conversion of the level-sensitive PMEIN# signal to the edge-
triggered PCI Express PM_PME message, the PMEIN# signal is polled every 256 ms by the PEX 8311
and a PCI Express PM_PME message is generated if PME# is asserted.
The PMEIN# signal is used only when the PEX 8311 is in Endpoint Mode.
3.7.1 Wakeup
The PEX 8311 asserts the WAKEOUT# signal or sends a PCI Express beacon for the following:
ƒ PMEIN# pin is asserted while link is in L2 state
ƒ PCI Express beacon is received while link is in L2 state
ƒ PCI Express PM_PME Message is received
A beacon is transmitted if the following are true:
ƒ PMEIN# pin is asserted while link is in L2 state
ƒ DEVSPECCTL register Beacon Generate Enable bit is set
ƒ PWRMNGCSR register PME Enable bit is set
The WAKEOUT# signal is used only when the PEX 8311 is in Endpoint mode.
3.8 Endpoint/Root Complex operation
The PEX 8311 RDK has been designed to demonstrate the operation of the PEX 8311 in Endpoint Mode.
While the PEX 8311 RDK has not been designed for Root Complex mode operation it is possible to
achieve limited Root Complex mode functionality. The following notes indicate how this may be achieved.
PLX has not tested operation of the board in Root Complex mode so customers who require this feature
do so at their own risk and must source and assemble the components themselves. PLX takes no
responsibility for boards damaged during this operation
To operate the PEX 8311 in Root Complex mode the PEX 8311 ROOT_COMPLEX# input should be
pulled low by removing R6 and adding R7. In Root Complex mode the local bus of the PEX 8311 will be
the upstream bus so some local intelligence will need to be added to act as the system host and
enumerate any downstream device. Local intelligence may be added by attaching a suitable processor to
either the POM (J3) connector, the test headers (LAH1-6) or by using the prototyping footprints.
When operating in Root Complex mode the internal clock (CLKIN) of the PEX 8311 must be supplied by
an external clock source. To use the clock source on the RDK remove R53 and assemble R52, R150,
C96, C97 and U13. The maximum operating frequency for U13 should be 66MHz.