•Phobos L1 (PhL1) is synchronized with the RF and have constant delay relative to the triggering bunch crossing. Upon receiving of the PhL1 the PhTiMeS calculates a region of interest (ROI) by subtracting the ‘L1 Settling Time’ from the current clock position. Obviously, the width of the ROI should cover spread of the hits plus one clock. All hits from the ROI will be transferred to an L1 output buffer (circular buffer, 256 word deep). Note. The maximum bunch filling of the RHIC is 112, in this case the distance between the possible bunch crossing is 3 RF ticks = 108 ns.