Time Requirements#
Time Synchronization#
Vehicle Time synchronization
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status: valid
security: NO
safety: QM
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The score::time feature shall synchronize the local clock with an external Grand Master using the gPTP protocol (IEEE 802.1AS). |
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Vehicle Time synchronization precision
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status: valid
security: NO
safety: QM
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The score::time feature shall synchronize the local time base with the Grand Master within a defined precision, based on the system setup (see Vehicle Time synchronization (feat_req__time__vehicle_time_sync)). Note:
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Vehicle Time base API
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status: valid
security: NO
safety: ASIL_B
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The score::time feature shall provide an API to access the synchronized Vehicle Time. Note: the ASIL-B level applies to the interface/module; the delivered value integrity is reflected by the time point qualifier (see Vehicle Time base time poin... (feat_req__time__vehicle_time_time_pt_qual)). |
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Vehicle Time base accuracy qualifier
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status: valid
security: NO
safety: ASIL_B
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The score::time feature shall provide an API to read the accuracy qualifier of the local synchronized time base. Note: qualifier shall reflect the accuracy of the local time base, e.g.
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Vehicle Time base time point qualifier
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status: valid
security: NO
safety: ASIL_B
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The score::time feature shall provide an API to read the time point qualifier of the local synchronized time base. Note: the qualifier tells the consumer whether the time point may currently be treated as ASIL-B data or only as QM data. This verdict comes from the integrity check established for the vehicle time (see Vehicle time value integrity (aou_req__feature_time__veh_time_integrity)); if no such check exists, the qualifier is QM. If that integrity check is integrated into score::time as an extension, the extension delivers its verdict through this qualifier (see Vehicle time integrity resu... (aou_req__feature_time__veh_time_qual_reflect)). |
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Vehicle Time control flow
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status: valid
security: NO
safety: ASIL_B
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The score::time feature shall provide an access its data via specified APIs in a fast and very efficient manner, avoiding, if possible, kernel calls, resource manager involvement and so on. For APIs see:
Use case: frequent access to the current synchronized time and its metadata by multiple clients within one ECU. |
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Vehicle Time synchronization logging
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status: valid
security: NO
safety: QM
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The score::time feature shall provide a mechanism to log the internal state of the synchronization process, to be able to debug and diagnose the synchronization process. Use case: Debugging and diagnostics of the time synchronization process. |
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HW clock synchronization to Vehicle Time
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status: valid
security: NO
safety: QM
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The score::time feature shall synchronize the local HW clock (e.g. NIC PHC) to Vehicle Time, enabling hardware timestamping of ingress and egress network frames. Note: the ownership of the HW clock discipline (score::time vs. the network/gPTP stack) is a system design choice. |
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Time Synchronization to absolute external sources#
score::time external synchronization
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status: valid
security: YES
safety: QM
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The score::time feature shall support synchronization with external time sources, such as UTC time from GPS. |
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Absolute Time base API
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status: valid
security: YES
safety: ASIL_B
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The score::time feature shall provide an API to read the Absolute Time base, synchronized to external time sources. Note: the ASIL-B level applies to the interface/module; the delivered absolute time value integrity remains QM. |
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Absolute Time base accuracy qualifier
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status: valid
security: YES
safety: QM
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The score::time feature shall provide an API to read accuracy qualifier of the Absolute Time base, synchronized to external time sources. Note: the inaccuracy could be indicated in the following manner
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Absolute Time base security qualifier
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status: valid
security: YES
safety: QM
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The score::time feature shall provide an API to read security qualifier of the Absolute Time base, synchronized to external time sources. Note: the security level might be indicated in the following steps
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Absolute Time synchronization status log
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status: valid
security: NO
safety: QM
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The score::time feature shall provide a mechanism to log the internal state of the Absolute Time synchronization process, to be able to debug and diagnose the synchronization process. |
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Local Clock#
High resolution clock API
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status: valid
security: NO
safety: ASIL_B
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The score::time feature shall provide an API to read the High-Resolution Steady Clock in nanoseconds resolution. Note: to which clock the high resolution clock is mapped, depends on the system design. Use case: such clocks might be used for time-critical applications, such as audio/video streaming, event logging, and diagnostics. |
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Monotonic clock API
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status: valid
security: NO
safety: ASIL_B
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The score::time feature shall provide an API to read monotonic, not adjustable clock value. |
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Testability#
score::time mocking APIs implementation
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status: valid
security: NO
safety: QM
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The score::time feature shall provide support for mocking its public interfaces, enabling unit, component and integration testing of applications. |
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