Data errors

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Common data blocks found in different events

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Bitflips

 Found in MCM headers (event counters)  Missing in the empty ADC masks and in the tracklet end markers ●

Conclusions, testpattern runs

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

1

Common blocks of data (1)

Common block of data found in 2 (or once in 3) events in the same run. No errors in the structure of the first event, broken structure of the second event.

Run 440_2 | | 440_2 Event 365 | | 392 EventCnt 357 | | 366 ROB 4 | <= 953395 => | 2 MCM 1 | <52> | 8 Link 12 | | 12

ZS

Run 466_1 | | 466_1 Event 2500 | | 3796 EventCnt 834 | | 1266 ROB 6 | <= 1050702 => | 6 MCM 7 | <44> | 6 Link 12 | | 12 <= distance in 32bit words =>

no ZS

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

2

Common blocks of data (2)

Common block of data from two adjacent events found in a later event. No errors in the structure of the first two event, broken structure of the third event.

Run 470_1 | | 470_1 Event 2686 | | 4012 EventCnt 51133 | | 51575 ROB 6 | <= 813091 => | 4 MCM 3 | <24> | 14 Link 12 | | 12 - continue on the next event Run 470_1 | | 470_1 Event 2689 | | 4012 EventCnt 51134 | | 51575 ROB 2 | <= 880527 => | 4 MCM 12 | <32> | 14 Link 12 | | 12 <= distance in 32bit words =>

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

3

Common blocks of data (3)

Common block of data found in 2 events in the two adjacent runs. No errors in the structure of the first event, broken structure of the second event.

Run 472_3 | | 473_1 Event 21691 | | 460 EventCnt 141163 | | 141546 ROB 4 | <= 926564 => | 6 MCM 10 | <49> | 0 Link 10 | | 10 <= distance in 32bit words => The consequences of these types of errors are wrong event counters, wrong last bits in the ADC data, breaks in the event structure.

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

4

Biterrors in event counter

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The event counters are correct in the previous and in the next event. This is not an internal TRAP error.

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The event counter (in the MCM header) is the first word sent by the MCM.

Frequently found errors in bits 0, 2 and 16 of the event counter (add 4 for the bit position in the output data).

Bit 20 (in event counter this is bit 16)

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run 474 in the first 5000/3 events in 47 cases the bit should be 0, but is 1 run 472 in the first 5000/3 events in 13 cases the bit should be 1, but is 0

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Bit 6 (in event counter this is bit 2) run 472 in the first 5000/3 events in 8 cases should be 0, but is 1

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run 473 and 466 in the first 5000/3 events in 4 cases should be 0, but is 1 No preferred ROBs or MCMs, only links 1..3 do not appear.

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

5

300

Biterrors in event counter, bit0

Bit 4 (in event counter this is bit 0) 0->1 1->0 250 200 150 100 50 0 435 440 445 450 455 Runs 460 465 470 475

The peaks do not correlate to any configuration changes, but may be T?

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

6

Missing biterrors in tracklet endmarker

In all analyzed runs the tracklet endmarker is 0xAAAAAAAA.

If the bit 4 (event counter bit 0) tends frequently to be 1 instead of 0, then one would expect to find tracklet endmarkers with set bit 4: 0xAAAAAAAA => 0xAAAAAA B A In such a case, the endmarker will be not stripped by the TRAP logic in the column merger, board merger and half-chamber merger, and will propagate as tracklet. A search for 0xAAAAAAAA xor 2 and NOT like this: n (n=0..31) in runs 437..474 (4.5GB) gave: 8 times …EA and 15 times …BA but as part of the pair of endmarkers 0xaaaaaa b a 0xaaaaaaaa 0xaaaaaaaa 0xaaaaaa b a 0xaaaaaaaa 0xaaaaaaaa This can happen only between HCM and ORI, in ORI or later, but not between the TRAPs.

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

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Examples of found biterrors in tracklet endmarker

Two typical examples of biterrors in tracklet endmarker 0x00000000 0x00000000 0x00000000 0x00000000 0x23b41d57 0xaaaaaaba 0xaaaaaaaa 0x83004049 0x7bf3c291 0xac0deaac 0xfe00000c 0x02409032 0x03009026 0xe30c989c 0xfe00000c 0x00000000 0xaaaaaaea 0xaaaaaaaa 0x830040cd 0x78cba251 0xbc0c989c 0xfe00000c

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

8

Missing biterrors in the empty adc masks

If bits 20 and 4 are frequently 1 instead of 0, then we should expect the same error in the empty ADC masks.

Bit 20 (16 ec) pattern 0xFE10000C 0xFE00000C Not found Bit 4 (0 ec) pattern 0xFE00001C 0xFE00000C Found only once, but as part of the known common block error.

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

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Conclusions

The block errors most probably are due to timing errors in the GTU FPGAs.

The reasons for the bitflip errors are still not very clear, they were for sure detected in the MCM headers, but not in the ADC masks (the two mostly transferred data words in case of zero suppression).

In order to understand more we need to test the complete readout chain with testpatterns, generated in the TRAPs.

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

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Reference

Used runs:

437_01 440_13 440_25 454_01 440_01 440_14 440_26 461_01 440_02 440_15 441_01 462_01 440_03 440_16 441_02 466_01 440_04 440_17 441_04 467_01 440_05 440_18 445_01 470_01 440_06 440_19 446_01 471_01 440_07 440_20 447_01 472_01 440_08 440_21 448_01 472_02 440_09 440_22 449_01 472_03 440_10 440_23 450_01 473_01 440_11 440_24 451_01 474_01 440_12

KIP TI, ALICE TRD status meeting 4 Dec 2007, GSI

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