1. 119 November ALTRO Trailer Format In case of a bad ALTRO trailer word the RCU will detect it and could correct it instead of skipping the whole channel. In order to have the complete information if the channel was corrupted it's necessary to mark this channel as corrected by the RCU. This could be easily done by a marker which should never occur in the real data. Example. ALTRO-TRAILER WORD (correct) Channel Data ALTRO-TRAILER WORD (correct) Channel Data MARKER: 0 3FF 0 3FF ALTRO-TRAILER WORD (corrected by RCU) ALTRO-TRAILER WORD (original corrupted trailer) Channel Data...... Torsten’s Proposal (1/2)

2. 219 November ALTRO Trailer Format The RCU knows the datasize of one channel so as long as the ALTRO trailer is correct the data will be in sync and will point in case of a corrupt trailer to the marker. The marker itself should never appear in real data. The chanel data consists of 4 10-bit words and can contain the following values: 1. ADC ADC ADC ADC -- see below 2. NS TB ADC ADC -- never matches since Number of samples (NS) should never be 0 and timebin 0x3FF is the first timebin and can contain only 1 ADC value 3. TB ADC ADC ADC -- see below 4. 2AA NS TB ADC -- never matches 5. 2AA 2AA NS TB -- never matches 6. 2AA 2AA 2AA NS -- never matches Since the ADC values are derived from the PASA and this does a gaussian correction the pattern 0 3FF 0 3FF should never occure. Maybe this is a little bit of overdoing it but it would allow some cross-checking to prevent getting out of sync. For correct data it would not change the datasize and only introduce 2 additional 40-bit words (Marker + correct ALTRO Trailer) for corrupted channels. Torsten’s Proposal (1/2)

3. 319 November ALTRO Trailer Format Slight variant to Torsten’s Porposal ALTRO data block The trailer is modified by the RCU Actual format Tr[39:26] ≡ 2AAA no meaning New format Tr[39:30] ≡ data format version (2AA at present) Tr[29:26] ≡ Error flag (binary distance > 2 ?) channel data block as modified by the RCU, in case of an error in the ALTRO Trailer word Channel Data Wrong Trailer Corrected Trailer