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B UILT -I N S ELF -T EST OF G LOBAL R OUTING R ESOURCES IN V IRTEX -4 FPGA S Jia Yao, Bobby Dixon, Charles Stroud and Victor Nelson Dept. of Electrical & Computer Engineering Auburn University
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North Atlantic Test Workshop2 J. Yao 5/15/08 2 Outline of Presentation Motivation and background Virtex-4 global routing resource Routing BIST Implementation for Virtex-4 FPGAs for Virtex-4 FPGAs Implementation results Application to Virtex-5 Summary
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North Atlantic Test Workshop3 Fault Simulation Results Stuck-at Fault Stuck-at value Feedback wires can be considered can be considered under test under test Bridging Fault Best approaches 8-bit maximum length sequence CAR sequence CAR cross-coupled parity J. Yao 5/15/08
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North Atlantic Test Workshop4 Cross-Coupled Parity Approach F LUT G LUT Podd Cd1 Cd0 F LUT G LUT Peven Cu1 Cu0 Slice 0 Slice 2 Slice 1 Slice 3 TPG (Te) count-up even parity TPG (To) count-down odd parity ORA (Oe) even parity ORA (Oo) odd parity 2 1 1 2 ORA even parity ORA odd parity G LUT Podd Cu1 Cu0 Pass /Fail G LUT Peven Cd1 Cd0 Pass /Fail Test Pattern Sequence Cu 1 Cu 0 PoCd 1 Cd 0 Pe 001110 010101 0011 111000 J. Yao 5/15/08
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North Atlantic Test Workshop5 Virtex-4 Global Routing Resources CLB Switch Box Slices (LUTs & FFs) PIPs Double/Hex lines N/S/E/W 10 wires BEG, MID, END Long Lines Switch Box N/S 2 BEG 0-9 N/S 2 MID 0-9 N/S 2 END 0-9 slices Long lines J. Yao 5/15/08
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North Atlantic Test Workshop6 BIST for Double lines (North and South) Test Pattern Sequence Cu 1 Cu 0 PoCd 1 Cd 0 Pe 001110 010101 0011 111000 Pass by 1 CLB into MID pass by 2 CLBs into END 6 wires under test (2 configs) 12 lines under test in parallel Alternate TPGs, ORAs position in adjacent CLBs. J. Yao 5/15/08
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North Atlantic Test Workshop7 Loopbacks South END-to-BEG Connections Loopback Connections At the edges of array via wires in the opposite direction till the opposite edge Example: north double lines loopback at the top edge J. Yao 5/15/08
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North Atlantic Test Workshop8 BIST for Double lines (East and West) Involve Non-CLB Columns END and BEG terminals in east and west directions are connected J. Yao 5/15/08
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North Atlantic Test Workshop9 Non-CLB Column Double Lines BIST for Non-CLB Column Double Lines TPGs and ORAs locate in adjacent CLB columns Use east/west double lines to connect adjacent CLB columns J. Yao 5/15/08
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North Atlantic Test Workshop10 BIST For Hex Lines Hex lines architecture pass by 3 CLBs into MID, by 6 CLBs into END more limitation of connections from hex lines to LUTs MID and END terminals share the same PIPs BIST for hex lines similar to double lines more configurations needed J. Yao 5/15/08
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North Atlantic Test Workshop11 Long Lines Architecture pass by 24 CLBs 5 wire segments 4 wires under test Bi-directional two end points: source or input other three stops: input only Orthogonal direction is tested simultaneously i i+1 i+6 i+7 i+12 i+13 i+18 i+19 i+24 i+25 J. Yao 5/15/08
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North Atlantic Test Workshop12 BIST for Long lines Oe Tcu Tcd Peven Cuo Cu1 Cu2 Peven CLB i CLB i+6 CLB i+12 CLB i+18 CLB i+24 G LUT Peven Cd0-3 Pass /Fail F LUT ORA even parity (Oe) TPG count-up even parity (Tcu) TPG count-down even parity (Tcd) Cu2 Cu1 Cu0PevenCd2 Cd1 Cd0Peven 0 0 001 1 11 0 0 111 1 00 0 1 011 0 10 0 1 101 0 01 10 1 10 1 0 100 1 01 1 1 000 0 11 1 1 110 0 00 CLB i+2 CLB i+1 CLB i CLB i+3 CLB i+4 CLB i+5 J. Yao 5/15/08
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North Atlantic Test Workshop13 Global Routing BIST Configurations Routing Resource Direction Total Configs NSEW CLB double lines 2222 8 Non-CLB column double lines224 CLB hex lines442212 Non-CLB column hex lines224 CLB long lines**112 Non-CLB column long lines112 Total BIST Configurations3232 J. Yao 5/15/08
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North Atlantic Test Workshop14 RAM DSPMIDDLE Actual Implementation Results I/O Cell J. Yao 5/15/08
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North Atlantic Test Workshop15 Application to Virtex-5 Global Routing Resource changed double lines, pent lines and long lines N/S/E/W BEG, MID, END half as the same, half as “L-shaped” which go in orthogonal direction as well 3 wires for each pattern in each direction instead of 10 long lines pass by 18 CLBs, four wires Our approach is adapted to Virtex-5 test for “L-shaped” double/pent lines J. Yao 5/15/08
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North Atlantic Test Workshop16 Summary Cross-coupled Parity is the best choice better fault coverage the most practical for actual implementation best choice for Virtex-5 BIST of Virtex-4 routing resources Program to generate BIST configurations automatically modified for V-5 J. Yao 5/15/08
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