diff --git a/algo/detectors/sts/UnpackSts.cxx b/algo/detectors/sts/UnpackSts.cxx
index eeb33bf047390c30084cfea30bf66dd66a32ef05..4d25a03410930148d46134572428fbaad96de958 100644
--- a/algo/detectors/sts/UnpackSts.cxx
+++ b/algo/detectors/sts/UnpackSts.cxx
@@ -26,10 +26,14 @@ namespace cbm::algo
// --- Output data
resultType result = {};
- // --- Current Timeslice time and TS_MSB epoch cycle
- fCurrentTsTime = tTimeslice;
- auto msTime = msDescr.idx; // Unix time of MS in ns
- fCurrentCycle = std::ldiv(msTime, fkCycleLength).quot;
+ // --- Current Timeslice start time in epoch units. Note that it is always a multiple of epochs
+ // --- and the epoch is a multiple of ns.
+ const uint64_t epochLengthInNs = fkEpochLength * fkClockCycleNom / fkClockCycleDen;
+ fCurrentTsTime = tTimeslice / epochLengthInNs;
+
+ // --- Current TS_MSB epoch cycle
+ auto const msTime = msDescr.idx; // Unix time of MS in ns
+ fCurrentCycle = std::ldiv(msTime, fkCycleLength).quot;
// ---Â Number of messages in microslice
auto msSize = msDescr.size;
@@ -46,18 +50,18 @@ namespace cbm::algo
// --- Interpret MS content as sequence of SMX messages
auto message = reinterpret_cast<const stsxyter::Message*>(msContent);
- // --- The first message in the MS is expected to be of type EPOCH and can be ignored
+ // --- The first message in the MS is expected to be of type EPOCH and can be ignored.
if (message[0].GetMessType() != stsxyter::MessType::Epoch) {
result.second.fNumErrInvalidFirstMessage++;
return result;
}
- // --- The second message must be of type ts_msb
+ // --- The second message must be of type ts_msb.
if (message[1].GetMessType() != stsxyter::MessType::TsMsb) {
result.second.fNumErrInvalidFirstMessage++;
return result;
}
- ProcessTsmsbMessage(message[1], result.second);
+ ProcessTsmsbMessage(message[1]);
// --- Message loop
for (uint32_t messageNr = 2; messageNr < numMessages; messageNr++) {
@@ -70,7 +74,7 @@ namespace cbm::algo
break;
}
case stsxyter::MessType::TsMsb: {
- ProcessTsmsbMessage(message[messageNr], result.second);
+ ProcessTsmsbMessage(message[messageNr]);
break;
}
default: {
@@ -112,10 +116,12 @@ namespace cbm::algo
channel = numChansPerModule - message.GetHitChannel() + 1;
}
- // --- Convert time stamp from clock cycles to ns
- uint64_t messageTime = (message.GetHitTimeBinning() * fkClockCycleNom + fkClockCycleDen / 2) / fkClockCycleDen;
- // --- Expand to time within timeslice
- messageTime += fCurrentEpochTime;
+ // --- Expand time stamp to time within timeslice (in clock cycle)
+ uint64_t messageTime = message.GetHitTimeBinning() + fCurrentEpochTime;
+
+ // --- Convert time stamp from clock cycles to ns. Round to nearest full ns.
+ messageTime = (messageTime * fkClockCycleNom + fkClockCycleDen / 2) / fkClockCycleDen;
+
// --- Correct ASIC-wise offsets
messageTime -= elinkPar.fTimeOffset;
// --- TODO: Add walk correction (depends on ADC)
@@ -130,25 +136,26 @@ namespace cbm::algo
// ----- Process an epoch (TS_MSB) message ------------------------------
- inline void UnpackSts::ProcessTsmsbMessage(const stsxyter::Message& message, UnpackStsMonitorData& monitor)
+ inline void UnpackSts::ProcessTsmsbMessage(const stsxyter::Message& message)
{
-
+ // The compression of time is based on the hierarchy epoch cycle - epoch - message time.
+ // Cycles are counted from the start of Unix time and are multiples of an epoch (ts_msb).
+ // The epoch number is counted within each cycle. The time in the hit message is expressed
+ // in units of the readout clock cycle relative to the current epoch.
+ // The ts_msb message indicates the start of a new epoch. Its basic information is the epoch
+ // number within the current cycle. A cycle wrap resets the epoch number to zero, so it is
+ // indicated by the epoch number being smaller than the previous one (epoch messages are
+ // seemingly not consecutively in the data stream, but only if there are hit messages in between).
auto epoch = message.GetTsMsbValBinning();
// --- Cycle wrap
if (epoch < fCurrentEpoch) fCurrentCycle++;
- // --- Update current epoch
- fCurrentEpoch = epoch;
- uint64_t epochTimeInCc = (fCurrentCycle * fkEpochsPerCycle + epoch) * fkEpochLength;
- if (epochTimeInCc >> 59 != 0) { // avoid overflow in 64 bit // TODO: Hard-coded number!
- monitor.fNumErrTimestampOverflow++;
- return;
- }
+ // --- Update current epoch counter
+ fCurrentEpoch = epoch;
- // --- Calculate epoch time in ns relative to timeslice start time
- fCurrentEpochTime = (epochTimeInCc * fkClockCycleNom + fkClockCycleDen / 2) / fkClockCycleDen;
- fCurrentEpochTime -= fCurrentTsTime;
+ // --- Calculate epoch time in clocks cycles relative to timeslice start time
+ fCurrentEpochTime = (fCurrentCycle * fkEpochsPerCycle + epoch - fCurrentTsTime) * fkEpochLength;
}
// --------------------------------------------------------------------------
diff --git a/algo/detectors/sts/UnpackSts.h b/algo/detectors/sts/UnpackSts.h
index 05989d375367dcc617c39b117e3a59c0f97c263f..ed1fd22a253c3c35a2b80fcf152f87e588966e4e 100644
--- a/algo/detectors/sts/UnpackSts.h
+++ b/algo/detectors/sts/UnpackSts.h
@@ -115,27 +115,29 @@ namespace cbm::algo
/** @brief Process an epoch message (TS_MSB)
** @param message SMX message (32-bit word)
- ** @param monitor Reference to monitor object
**/
- void ProcessTsmsbMessage(const stsxyter::Message& message, UnpackStsMonitorData& monitor);
+ void ProcessTsmsbMessage(const stsxyter::Message& message);
+
+
+ private: // members
+ uint64_t fCurrentTsTime = 0; ///< Unix time of timeslice in units of epoch length
+ uint64_t fCurrentCycle = 0; ///< Current epoch cycle
+ uint32_t fCurrentEpoch = 0; ///< Current epoch number within epoch cycle
+ uint64_t fCurrentEpochTime = 0; ///< Current epoch time relative to timeslice in clock cycles
+ UnpackStsPar fParams = {}; ///< Parameter container
+ /** Number of TS_MSB epochs per cycle **/
+ static constexpr uint64_t fkEpochsPerCycle = stsxyter::kuTsMsbNbTsBinsBinning;
- private: // members
- uint64_t fCurrentTsTime = 0; ///< Unix time of timeslice in ns
- uint64_t fCurrentCycle = 0; ///< Current epoch cycle
- uint32_t fCurrentEpoch = 0; ///< Current epoch number within epoch cycle
- uint64_t fCurrentEpochTime = 0; ///< Unix time of current epoch in clock cycles
+ /** Length of TS_MSB epoch in clock cycles **/
+ static constexpr uint64_t fkEpochLength = stsxyter::kuHitNbTsBinsBinning;
- static constexpr uint64_t fkEpochsPerCycle = stsxyter::kuTsMsbNbTsBinsBinning; ///< TS_MSB epochs per epoch cycle
- static constexpr uint64_t fkEpochLength =
- stsxyter::kuHitNbTsBinsBinning; ///< Length of TS_MSB epoch in clock cycles
- static constexpr uint32_t fkClockCycleNom = stsxyter::kulClockCycleNom; ///< Clock cycle nominator [ns]
- static constexpr uint32_t fkClockCycleDen = stsxyter::kulClockCycleDen; ///< Clock cycle denominator
- static constexpr uint64_t fkCycleLength =
- (fkEpochsPerCycle * fkEpochLength * fkClockCycleNom) / fkClockCycleDen; ///< Epoch cycle length in ns
+ /** Clock cycle nominator [ns] and denominator. The clock cycle in ns is nominator / denominator. **/
+ static constexpr uint32_t fkClockCycleNom = stsxyter::kulClockCycleNom;
+ static constexpr uint32_t fkClockCycleDen = stsxyter::kulClockCycleDen;
- //std::unique_ptr<UnpackStsPar> fParams = nullptr; ///< Parameter container
- UnpackStsPar fParams = {}; ///< Parameter container
+ /** Epoch cycle length in ns **/
+ static constexpr uint64_t fkCycleLength = (fkEpochsPerCycle * fkEpochLength * fkClockCycleNom) / fkClockCycleDen;
};