Hot Plug Support
PLX Technology, Inc.
9.3
Hot Plug Interrupts
Each Hot Plug Controller supports Hot Plug interrupt generation on the following events:
• Attention Button Pressed
• Power Fault Detected
• MRL Sensor Changed
• Presence Detect Changed
• Command Completed
Hot Plug interrupts can be signaled by in-band INTx or MSI messages. Only one interrupt mechanism
can be selected, and all Hot Plug ports must use the same mechanism.
INTx interrupts are enabled if:
• INTA messages are enabled (Command register Interrupt Disable bit, offset 04h[10]=0) and,
• MSI is disabled (Message Control register MSI Enable bit, offset 48h[16]=0)
MSI interrupts are enabled if:
• INTA messages are disabled (Command register Interrupt Disable bit, offset 04h[10]=1) and,
• MSI is enabled (Message Control register MSI Enable bit, offset 48h[16]=1)
Depending on the downstream port power state, a Hot Plug event can generate a system interrupt or
PME. When a PEX 8532 downstream port is in the D0 power state, Hot Plug events generate a system
interrupt; when not in the D0 state, a PME interrupt message is generated by Hot Plug events. The
Slot Status register Command Completed bit (offset 80h[20]) does not generate a PME interrupt
message. When the system is in Sleep mode, Hot Plug operation uses PME logic to wake up the system.
9.4
Hot Plug Controller Power-Up/Down Sequence
If a Transparent downstream port is enabled, the port’s Hot Plug Controller can power-up or
power-down the slot. This section describes how this process occurs.
9.4.1
Slot Power-Up Sequence
If a downstream port is connected to a slot, that port’s Hot Plug Controller can power up the slot, with or
without an external serial EEPROM. Hot Plug Controller sequencing is determined by the states of the
following bits:
• Slot Capabilities register Power Controller Present bit (offset 7Ch[1])
• Slot Capabilities register MRL Sensor Present bit (offset 7Ch[2])
(MRL is Manually operated Retention Latch)
• Slot Control register Power Controller Control bit (offset 80h[10])
and the HP_MRLx# input state, if the MRL Sensor Present bit is set to 1. Hot Plug-configurable features
are programmable only by the serial EEPROM.
122
ExpressLane PEX 8532AA/BA/BB/BC 8-Port/32-Lane Versatile PCI Express Switch Data Book
Copyright © 2007 by PLX Technology, Inc. All Rights Reserved – Version 1.6
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