Untitled :: RISC-V Ratified Specifications Library

4.1. N-Trace Specific Trace Controls

This chapter describes how fields and bits from Trace Encoder control registers (named using trTe… pattern) are influencing N-Trace encoder and N-Trace protocol messages. N-Trace specific clarifications, in addition to description in RISC-V Trace Control Interface specification are provided.

The table below does not provide names of Trace Encoder control registers as names of bits/fields used in Trace Control Interface are unique.

Table 1. Trace Encoder Parameters and Controls
Trace Control Field	Applicability	Description
trTeActive	Required	See RISC-V Trace Control Interface Specification.
trTeEnable	Required	See RISC-V Trace Control Interface Specification.
trTeInstTracing	Required	See RISC-V Trace Control Interface Specification.
trTeEmpty	Required	See RISC-V Trace Control Interface Specification.
trTeInstMode	Required	3: Generate instruction trace using BTM (Branch Trace Messaging) mode. 6: Generate instruction trace using HTM (History Trace Messaging) mode. 0, 7: See RISC-V Trace Control Interface Specification. 1-2, 4-5: Reserved for future N-Trace use. At least a value of 3 or 6 must be settable.
trTeContext	Optional	Controls generation of Ownership messages.
trTeInstTrigEnable	Optional	See RISC-V Trace Control Interface Specification.
trTeInstStallOrOverflow	Required	See RISC-V Trace Control Interface Specification.
trTeInstStallEna	Optional	See RISC-V Trace Control Interface Specification.
trTeInhibitSrc	Optional	Controls generation of SRC field.
trTeInstSyncMode	Required	Controls generation of Synchronizing Messages with SYNC field=2.
trTeInstSyncMax	Required	Controls generation of Synchronizing Messages with SYNC field=2.
trTeFormat	Required	Must be set to 1 (which denotes N-Trace format).
trTeVerMajor	Required	See RISC-V Trace Control Interface Specification.
trTeVerMinor	Required	See RISC-V Trace Control Interface Specification.
trTeCompType	Required	See RISC-V Trace Control Interface Specification.
trTeProtocolMajor	Required	Must be 1 to encode this version (1.0) of N-Trace protocol. Value different than 1 is considered a non-compatible version and must be rejected by the trace tool if it is only compliant with version 1.0 of the N-trace protocol.
trTeProtocolMinor	Required	Must be 0 to encode this version (1.0) of N-Trace protocol. When trTeProtocolMajor is 1, values other than 0 are considered down compatible extension and should be accepted by the trace tool. Any future non-compatible feature should be specifically enabled (by new control bits), so older tools (which never set these new bits) should work with it.
trTeInstNoAddrDiff	Not applicable	Must be hard coded as 0.
trTeInstNoTrapAddr	Not applicable	Must be hard coded as 0.
trTeInstEnSequentialJump	Optional	See Sequential Jump Optimization chapter.
trTeInstEnImplicitReturn	Optional	See Implicit Return Optimization chapter.
trTeInstEnBranchPrediction	Not applicable	Must be hard coded as 0.
trTeInstEnJumpTargetCache	Not applicable	Must be hard coded as 0.
trTeInstImplicitReturnMode	Optional	See Implicit Return Optimization chapter.
trTeInstEnRepeatedHistory	Optional	See Repeated History Optimization chapter.
trTeInstEnAllJumps	Optional	See RISC-V Trace Control Interface Specification.
trTeInstExtendAddrMSB	Optional	See Virtual Addresses Optimization chapter.
trTeSrcID	Optional	Controls generation of SRC field.
trTeSrcBits	Optional	Controls generation of SRC field.
trTeInstFilters	Optional	See RISC-V Trace Control Interface Specification.
trTeDataImplemented	Not applicable	Must be 0 as IEEE-5001 Nexus Standard data trace messages are not part of version 1.0 of N-Trace specification.
Other trTeData…	Not applicable	Must be 0 as IEEE-5001 Nexus Standard defines data trace messages, future versions of N-Trace may allow these (as an optional extension).
All trTeTrig…	Optional	See RISC-V Trace Control Interface Specification.
All trTeFilter…	Optional	See RISC-V Trace Control Interface Specification.
All trTeComp…	Optional	See RISC-V Trace Control Interface Specification.
trTsEnable	Optional	Part of potentially shared Timestamp Unit controls generation of TSTAMP field. See RISC-V Trace Control Interface Specification for details of the Timestamp Unit.