Potential issue with the BC0 alignement
While doing some tests with the EMTF yesterday, we noticed a strange behavior in the BC0 timing when the BCN offset was set to a "negative" value, in particular -1 BX, i.e. a value of 3563 in the CONTROL.TTC.BXN_OFFSET
register.
Can it be that bxn_ovf
is not going high properly if bxn_counter
is reset to 3564 (https://gitlab.cern.ch/emu/0xbefe/-/blob/optohybrid-4g/gem/hdl/oh_fe/control/ttc.vhd#L82). Then, the local BC0 would be issued when the bxn_counter
counter wraps up, completely shifted in time with respect to the expectations?
We have applied a global offset on both the GEM and EMTF sides to avoid the negative BC0 offset case, so this issue is low priority.