Electronics for Physicists Lecture 16 Programmable Logic

Programmable Digital Logic + FPGA December 2018 Electronics for physicists

PROM PROM: programmable sum of products with predefined products PROM before programming PROM: programmable sum of products with predefined products December 2018 Electronics for physicists

Electronics for physicists PROM December 2018 Electronics for physicists

PROM PROM after programming December 2018 Electronics for physicists

Electronics for physicists December 2018 Electronics for physicists

PLAs and PALs PAL PLA In PLAs, both the AND and the OR matrix can be programmed. In PALs, only the AND matrix can be programmed. December 2018 Electronics for physicists

Electronics for physicists Complex PLDs (CPLD) Structure of a CPLD Programmable SPLDs Programmable interconnects Some CPLDs keep memory settings after power-off Zoom in December 2018 Electronics for physicists

FPGA – Field Programmable Gate Array FPGA: Sea of programmable islands in an ocean of interconnects 80 – 90% of FPGA are interconnects. FPGAs are much more powerful and expensive than CPLDs December 2018 Electronics for physicists

Electronics for physicists FPGA building blocks Logic cells: MUX, flipflops, SRAM Interconnects: programmable routing switches, input connection blocks Clock distribution logic Block RAM (BRAM) Dedicated Digital Signal Processors (DSPs) Medium- and high-speed data transceivers (6 Mb/s - 33 Gb/s lines) High-end FPGAs can receive and send several Terabit/s ! „Soft“ or „hard“ micro processors ADC for monitoring operation temperature and voltages … December 2018 Electronics for physicists

Logic gates = Truth table = Look-up Table Look-up table (LUT) Logic gates = Truth table = Look-up Table December 2018 Electronics for physicists

Illustration of a slice with two logic cells December 2018 Electronics for physicists

Electronics for physicists Logic block (CLB) December 2018 Electronics for physicists

A logic cell in operation December 2018 Electronics for physicists

Electronics for physicists Example: SLICEL Note that: LUT outputs can be connected there are different types of MUXs the carry structure to connect different slices December 2018 Electronics for physicists

Illustration of interconnect logic Note the differences between programmable input connection blocks and routing switches long and short connections December 2018 Electronics for physicists

Electronics for physicists ASIC costs Integrated circuit tier structure Many metal layers for power (thick metal) and general connectivity (thin metal) Costs of masks range from 100 k€ to several M€ for modern processes. Multi-project wafer (MPW) still cost ~10 k€ for a few chips or just one chip of a few mm2 area. December 2018 Electronics for physicists

Electronics for physicists Gate arrays (GAL) Prefabricated set of transistors and logic gates Custom metal layers Gate arrays offer low-density circuits at reduced costs Basic cells Double column array December 2018 Electronics for physicists

Electronics for physicists FPGA design flow Functional design in VHDL. Then functional (RTL) simulation Synthesis: interpretation of VHDL code and mapping to FPGA building blocks (LUTs, MUX, registers, ….) => Netlist. Then timing analysis Implementation: Translate, map, place & route => bitstream FPGA configuration: download bit stream into FPGA and run! December 2018 Electronics for physicists

Electronics for physicists ML605 development board December 2018 Electronics for physicists

Virtex-6 Pinout (FF1155 Package) ~ 1000 connections high-speed I/O high power density for compute intense use Designing an FPGA board is involved! December 2018 Electronics for physicists

Electronics for physicists Why use FPGAs ? High computing power through parallel processing Acess to latest transistor technologies Energy efficiency in comparison to CPUs and GPUs Affordable in comparison with ASIC development Relatively short design cycles Firmware can be updated! FPGAs are heavily used in data acquisition and trigger systems December 2018 Electronics for physicists

Disadvantages of FPGAs for detector instrumentation ? FPGA are essentially digital devices with no analog functionality Power consumption is still high in comparison to ASICs FPGAs are not necessarily radiation-tolerant FPGAs are bulky On-detector logic does not always need to be „intelligent“ FPGAs are not used as front-end electronics December 2018 Electronics for physicists

Comparison FPGA & GPU &CPU December 2018 Electronics for physicists