PCIE SPEC 4.0（PCI-SIG ENGINEERING CHANGE NOTICE）
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Page 1
PCI-SIG ENGINEERING CHANGE NOTICE
TITLE:
Enhanced PCIe Precision Time Measurement (ePTM)
DATE:
Introduced: 2 May 2018
Updated: 8 January 2019
Final Approval: 10 January 2019
AFFECTED DOCUMENT:
PCI Express 4.0 Base Specification
SPONSOR:
Intel Corporation
Part I
1.
Summary of the Functional Changes
ePTM is an improvement on the existing Precision Time Measurement capability that
provides improved detection and handling of error cases. ePTM quickly identifies and
resolves errors that may cause clocks to become desynchronized.
2.
Benefits as a Result of the Changes
A design implementing ePTM will benefit from improved detection and handling of error
cases that would otherwise cause clocks to become desynchronized.
3.
Assessment of the Impact
ePTM only affects designs that utilize PTM. See 4 and 5 for additional details.
4.
Analysis of the Hardware Implications
ePTM is fully backwards compatible with existing PTM implementations. PTM and ePTM
implementations are interoperable. PTM enabled implementations receive the improved
error detection of ePTM when connected to a ePTM implementation.
5.
Analysis of the Software Implications
ePTM uses the same software interface as PTM. Existing PTM software should be
compatible with new ePTM implementations. No software changes should be necessary
to enable ePTM.
The only change visible to software is the addition of the ePTM Capable bit to the PTM
Extended Capability.
6.
Analysis of the C&I Test Implications
This ECN allocates previously reserved bits and requires the creation of new tests for the
new register fields. ePTM Asserts additional operational requirements on PTM
Requesters and PTM Responders. These additional requirements are a superset of the
existing PTM requirements. New C & I tests would be required if it is desirable to extend
C & I coverage to explicitly evaluate these new requirements.
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