Uli Schäfer 1 FPGAs for high performance – high density applications Intro Requirements of future trigger systems Features of recent FPGA families 9U * 40cm ATCA µTCA/AMC

Uli Schäfer 2 Intro : FPGA basics Large array of logic cells ~100k combinatorial : map any 4-variable equation into 4-input lookup table (LUT) sequential : flip-flop (FF) Interconnect ‘wires’ : segmented routing switch boxes connecting wires and logic cells dedicated global clock trees into all cells I/O pads route internal signals to pins define signal standard Clock management : condition the incoming clocks and generate multiples and fractions phase lock loop (PLL) delay lock loop (DLL) Cores RAM blocks for data storage Many other cores introduced in recent years, see below… Functionality of FPGA is defined upon power up by reading in a configuration data stream from non-volatile memory

Uli Schäfer 3 Higher granularity along with the need to keep fraction of duplicated channels at reasonable level requires higher density designs (higher channel count per FPGA and per module) Typical form factors and therefore card edges tend to get smaller: current L1calo ‘standard’ is 9U*400mm Telecom standards :ATCA: 8U * 280mm µTCA (AMC): 73.5 * 180.6mm Narrower data paths, but 10/12.5 Gbps per link Single ended data transmission stretched to limits at data rates and signal standards employed on current L1calo modules  go differential FPGA features in demand: on-chip high-speed serial links ( incoming trigger tower data ) differential high-speed data buses ( FIO ) logic resources (fabric) arithmetic units in case more demanding algorithms required suitable pinout and I/O properties for high density / high speed designs (signal integrity) Requirements of future L1calo processors

Uli Schäfer 4 Recent FPGA features/improvements Increase in clock speed Increase in logic resources (fabric) Increase in block memory Further hard cores: Processors Gbps serializer/deserializer units for parallel source synchronous data transmission (clock forwarding) Multi-Gbps links with embedded clock DSP / arithmetic circuitry I/O Differential high-speed standards (LVDS,PECL,…) Low voltage single ended Internal termination differential : 100Ω single ended : ‘programmable’ impedance On-chip bypass capacitors and signal integrity-optimised pinout

Uli Schäfer 5 Resources by manufacturer (*) All FPGA families have some means of phase adjustment (L,X) or multi-phase sampling (A) on their input lines, as well as SerDes. Not all features available on all I/O lines Virtex-4 have 6.5 Gbps serial links Altera Stratix III Lattice SC Xilinx Virtex-5 Global clocks MHz Clock management PLL1286 Clock management DLL012 Serial links (IIGX)3.83.7Gb/s Parallel differential I/O w. full speed / SerDes / phase (*) pairs Gb/s

Uli Schäfer 6 Lattice SC input delay control 144 tap delay unit, 40ps/tap 9-tap sampling within a window allows for calculation of optimum sampling point and automatic delay adjustment Available on every other differential pair only

Uli Schäfer 7 Xilinx Virtex-5 source synchronous interface (Gbps, double data rate) SerDes and programmable delay unit available in all I/O pads No hard core phase aligner, use soft core (fabric) to track data Eliminate cycle-to-cycle jitter at source with a PLL Due to the DLL the data are clocked into the deserialiser with a clock edge generated just a few ticks before the data bit  Low frequency jitter doesn’t matter

Uli Schäfer 8 Xilinx serial links (MGT) 3.7 Gbps serial link, low power 100mW/ch up to 24 channels per device  Data rate and channel count match SNAP12 optical link Transmitter:programmable signal level pre-emphasis Receiver: equalization Latency (RX+TX) : minimum of 12.5 ticks of byte clock byte clock could be as high as 320 MHz for a 40 MHz based system 40ps reference clock jitter requirement Re-design LHC clock distribution Use jitter attenuators (silabs.com) Go asynchronous Use local Xtal Require re-synchronisation to LHC clock (latency !) Allow for standard data rates / standard components

Uli Schäfer 9 Xilinx Virtex-5 resources (maximum) Resource Virtex-5(in XCV1000E) 6-input LUTs:200k(25k*4-input) Flipflops:200k(25k) Distributed RAM : 3.4 Mb(400kb) Block RAM :11.6Mb(400kb) “DSP” 25*18 bit multiplier/accumulator:640 PCI Express endpoint 1 Ethernet MAC (with internal or external PHY) 4

Uli Schäfer 10 Summary / Outlook Logic density gone up considerably. A single FPGA is equivalent to almost a full L1calo processor module Current FPGA families allow for high data rates on both ‘parallel’ and high-speed serial links Aggregate bandwidth is higher on ‘parallel’ links Xilinx Virtex-5 has same high-speed I/O resources on all user pins and is therefore particularly useful for typical trigger circuitry : many-in  few-out On-chip links with embedded clock do have surprisingly low latency but might need additional synchroniser stages due to jitter requirements Xilinx development boards ML506/ML555 available  let’s start work. Explore synchronous / asynchronous schemes