Tests of the Fully Loaded CSC Track Finder Backplane M.Matveev S.-J. Lee Rice University Alex Madorsky University of Florida 2 May 2005

Goals of the Test Check all electrical connections between Muon Sorter and 12 Sector Processors (384 “data” + 24 “winner” lines) slots Check timing and quality of GTLP signals on backplane at 80Mhz This is actually the first time we are able to check the fully loaded Track Finder backplane Measure the “safe window” of data latching on Muon Sorter board with 12 Muon Testers (replacement of SP) Develop and test the software that will be used for future integration tests

Muon Tester Board Designed at Rice in 2004 as a replacement for TMB and SP specifically for peripheral and Track Finder backplane tests

Track Finder Crate Under Tests at Rice

Software Functionality Can load random sets of patterns (510 frames) into any number of Muon Testers (1..12) and send them out to Muon Sorter on broadcast command Can adjust 80Mhz clock on MS input with 100 ps (internal DLL) or 250 ps (external delay chip) step Read data from FIFO_B and FIFO_C after sorting and verify against expected values Firmware Functionality In addition to “old” MS functions the MS logic can now mask data from any SP on its inputs

Measurements of the “Safe Window” in March Safe window = 4 ns when MT1-MT6 are sending data simultaneously (192 lines switching at 80Mhz) Safe window = 2.5 ns when MT7-MT12 are sending data simultaneously (192 lines switching at 80Mhz) Safe window = 1 ns when all MT1-MT12 are sending data simultaneously (384 lines switching at 80Mhz) Unacceptable – too narrow. Why?

Yellow: X25:B21 (SP4_29). Note X25:C21 is SP4_30. Blue: X25:D15 (SP4_0). Note X25:C15 is GND. Conditions: all 12 Muon Testers are sending data to Muon Sorter (384 lines are switching simultaneously) Track Finder Backplane Waveforms (Example)

One of 4 connectors on MS slot (the other 3 are similar) SP- to - MS connector Track Finder Backplane Yellow waveform on previous slide Blue waveform on previous slide

Observations When 384 MT-to-MS lines are switching simultaneously at 80Mhz, the quality of signals on lines A[i], B[i], D[i] and E[i] of the backplane connectors is acceptable if C[i] is GND (i=1…25) on both MS and SP slots. Signal distortion is significant if C[i] is assigned to signal or +1.5V. 240 signals out of 384 are at risk We haven’t seen such a problem in the peripheral crate. Note: most C[i] pins on Muon Port Card and TMB slots are grounded Signal distortion increases gradually with the number of switching sources That explains why the “safe window” is shrinking also gradually Ccb_cmd_strobe line (the most important bussed line) is OK for any number of switching data sources SP11 signals reception on MS is affected by winner bits training pattern (winner bits transmitters are located near SP11 receivers, 24 bits)

Yellow: X39:A10 (TMB1_Data4) Blue: X39:B14 (TMB1_Data21) Conditions: all 9 TMBs are sending data to MPC (288 lines are switching simultaneously) Example of the Peripheral Backplane Waveform

Steps taken to fix the problem on the existing prototypes Backplane: Additional grounding provided (copper foil) on both sides Grounding pins for the Muon Sorter connectors added Muon Sorter : Connector shields added, attached to MS ground as well as possible Training patterns disabled (24 winner bits switching at 40 MHz)

Track Finder Backplane after modification (rear view)

Results after prototype modifications Safe data reception window: 3.75 ns – the same as in the peripheral crate Such window is considered acceptable (taking into account the difference in delays in Tx, Rx and backplane) On both ends of safe window, the errors appear from multiple sources simultaneously – no single bad source The system is working as expected

Track Finder Backplane Waveforms (same signals) Yellow: X25:B21 (SP4_29). Note X25:C21 is SP4_30. Blue: X25:D15 (SP4_0). Note X25:C15 is GND. Conditions: all 12 Muon Testers are sending data to Muon Sorter (384 lines are switching simultaneously) Before backplane modificationAfter backplane modification Threshold

Backplane revision 2 modifications 1.All transmission lines to be moved to internal layers, between two ground layers (stripline) 2.Top and bottom layers flooded with ground 3.7-row shielded connectors will be used in MS slot, all C-row pins grounded 4.7-row shielded connectors will be used in SP slot 5.Special 1.5 V distribution layer to MS, bypass capacitors 6.Grounded mounting holes

Muon Sorter revision 2 modifications 1.Connectors will be replaced with shielded versions, pin assignment to match rev 2 backplane 2.At least 2 Ground layers, dedicated plane layers for 3.3V and 1.5 V distribution 3.All transmission lines to be moved to internal layers, between two ground layers (stripline) 4.Top and bottom layers flooded with ground 5.Winner bit GTLP transmitters will be shifted away from receivers 6.Clock line will be provided for GTLP receivers

Conclusion First prototypes of the TF backplane and Muon Sorter did not provide a reliable transmission of point-to-point signals at 80Mhz After modifications, the system works as expected Muon Sorter board and Track Finder backplane designs have to be modified, and the new boards produced Required modifications are well understood and tested