Global Trigger Finds Correct BX Assume we have a set of halo event from beam bunch 900. We will see a CSC pulse peak at a fixed offset to the beam clock edge in each chamber. This offset for the pulse beam to beam clock edge remains constant for all halos from this bunch. Bx Pulse Peak SCA Sampling BX number 897 898 889 900 901 902 903 904 Global Trigger Finds Correct BX In the first case assume the L1A Global Trigger finds the correct beam crossing number 900. The CFEB will calculate the L1A phase bit as 1 since it is in the second half of the SCA sample. The CFEB will choose capacitors to store starting at Bx 889. Pulse Peak Bx SCA Sampling BX number 897 898 889 900 901 902 903 904 SCA Start L1A Pulse Peak Time

Global Trigger Finds Wrong BX In the second case assume the L1A Global Trigger finds the wrong beam crossing number 901. The CFEB will calculate the L1A phase bit as 0 since it is in the first half of the SCA sample. The CFEB will choose capacitors to store starting at Bx 901. The pulse peak time will shift by 50 nsec. Pulse Peak Bx SCA Sampling BX number 897 898 889 900 901 902 903 904 SCA Start L1A Pulse Peak Time