Specification Sheet

Datasheet, Volume 2 of 2 161
DMIBAR Registers
9:7
0h
RWS_V
txmargin: Transmit Margin: This field controls the value of the non-deemphasized
voltage level at the Transmitter pins. This field is reset to 000b on entry to the LTSSM
Polling.Configuration substrate.
000: Normal operating range
001: 800-1200 mV for full swing and 400-700 mV for half-swing
010 - (n-1): Values should be monotonic with a non-zero slope. The value of n should
be greater than 3 and less than 7. At least two of these should be below the normal
operating range
n: 200-400 mV for full-swing and 100-200 mV for half-swing
n -111: reserved
Default value is 000b.
Components that support only the 2.5GT/s speed are permitted to hardwire this bit to
0b.
When operating in 5GT/s mode with full swing, the deemphasis ratio should be
maintained within +/- 1dB from the specification defined operational value (either -3.5
or -6 dB).
6
0h
RWS
selectabledeemphasis: Selectable De-emphasis: When the Link is operating at 5GT/
s speed, selects the level of de-emphasis. Encodings:
1b: -3.5 dB
0b: -6 dB
Default value is implementation specific, unless a specific value is required for a
selected form factor or platform.
When the Link is operating at 2.5GT/s speed, the setting of this bit has no effect.
Components that support only the 2.5GT/s speed are permitted to hardwire this bit to
0b.
5
0h
RWS
HASD: Hardware Autonomous Speed Disable: When set to 1b this bit disables
hardware from changing the link speed for reasons other than attempting to correct
unreliable link operation by reducing link speed.
4
0h
RWS
EC: Enter Compliance: Software is permitted to force a link to enter Compliance mode
at the speed indicated in the Target Link Speed field by setting this bit to 1b in both
components on a link and then initiating a hot reset on the link.
3:0
1h
RWS
TLS: Target Link Speed: For Downstream Ports, this field sets an upper limit on Link
operational speed by restricting the values advertised by the Upstream component in
its training sequences. The encoding is the binary value of the bit in the Supported
Link Speeds Vector (in the Link Capabilities 2 register) that corresponds to the desired
target Link speed. All other encodings are reserved. For example, 5.0 GT/s
corresponds to bit 2 in the Supported Link Speeds Vector, so the encoding for a 5.0
GT/s target Link speed in this field is 0010b.
If a value is written to this field that does not correspond to a supported speed (as
indicated by the Max Link Speed Vector), the result is undefined. The default value of
this field is the highest Link speed supported by the component (as reported in the
Max Link Speed field of the Link Capabilities register) unless the corresponding
platform/form factor requires a different default value.
For both Upstream and Downstream Ports, this field is used to set the target
compliance mode speed when software is using the Enter Compliance bit to force a
Link into compliance mode. For a Multi-Function device associated with an Upstream
Port, the field in Function 0 is of type RWS, and only Function 0 controls the
components Link behavior. In all other Functions of that device, this field is of type
RsvdP.
Bit
Range
Default &
Access
Field Name (ID): Description