Presence Detection; Message Generation; Attention Button Detection - Intel 6 SERIES CHIPSET - DATASHEET 01-2011 Datasheet

Functional Description
5.2.4.1

Presence Detection

When a module is plugged in and power is supplied, the physical layer will detect the
presence of the device, and the root port sets SLSTS.PDS (D28:F0/F1/F2/F3/F4/
F5:Offset 5Ah:Bit 6) and SLSTS.PDC (D28:F0/F1/F2/F3:Offset 6h:Bit 3). If SLCTL.PDE
(D28:F0/F1/F2/F3/F4/F5/F6/F7:Offset 58h:Bit 3) and SLCTL.HPE (D28:F0/F1/F2/F3/
F4/F5/F6/F7:Offset 58h:Bit 5) are both set, the root port will also generate an
interrupt.
When a module is removed (using the physical layer detection), the root port clears
SLSTS.PDS and sets SLSTS.PDC. If SLCTL.PDE and SLCTL.HPE are both set, the root
port will also generate an interrupt.
5.2.4.2

Message Generation

When system software writes to SLCTL.AIC (D28:F0/F1/F2/F3/F4/F5/F6/F7:Offset
58h:Bits 7:6) or SLCTL.PIC (D28:F0/F1/F2/F3/F4/F5/F6/F7:Offset 58h:Bits 9:8), the
root port will send a message down the link to change the state of LEDs on the module.
Writes to these fields are non-postable cycles, and the resulting message is a postable
cycle. When receiving one of these writes, the root port performs the following:
• Changes the state in the register.
• Generates a completion into the upstream queue
• Formulates a message for the downstream port if the field is written to regardless
of if the field changed.
• Generates the message on the downstream port
• When the last message of a command is transmitted, sets SLSTS.CCE (D28:F0/F1/
F2/F3/F4/F5/F6/F7:Offset 58h:Bit 4) to indicate the command has completed. If
SLCTL.CCE and SLCTL.HPE (D28:F0/F1/F2/F3/F4/F5/F6/F7:Offset 58h:Bit 5) are
set, the root port generates an interrupt.
The command completed register (SLSTS.CC) applies only to commands issued by
software to control the Attention Indicator (SLCTL.AIC), Power Indicator (SLCTL.PIC),
or Power Controller (SLCTL.PCC). However, writes to other parts of the Slot Control
Register would invariably end up writing to the indicators and power controller fields.
Hence, any write to the Slot Control Register is considered a command and if enabled,
will result in a command complete interrupt. The only exception to this rule is a write to
disable the command complete interrupt which will not result in a command complete
interrupt.
A single write to the Slot Control register is considered to be a single command, and
hence receives a single command complete, even if the write affects more than one
field in the Slot Control Register.
5.2.4.3

Attention Button Detection

When an attached device is ejected, an attention button could be pressed by the user.
This attention button press will result in a the PCI Express message
"Attention_Button_Pressed" from the device. Upon receiving this message, the root
port will set SLSTS.ABP (D28:F0/F1/F2/F3/F4/F5/F6/F7:Offset 5Ah:Bit 0).
If SLCTL.ABE (D28:F0/F1/F2/F3/F4/F5:Offset 58h:bit 0) and SLCTL.HPE (D28:F0/F1/
F2/F3/F4/F5/F6/F7:Offset 58h:Bit 5) are set, the Hot-Plug controller will also generate
an interrupt. The interrupt is generated on an edge-event. For example, if SLSTS.ABP is
already set, a new interrupt will not be generated.
Datasheet 121