Electronics for Physicists Lecture 16 Programmable Logic Programmable

Electronics for Physicists Lecture 16 Programmable Logic

Programmable Digital Logic + FPGA December 2018 Electronics for physicists Marc Weber - KIT 2

PROM before programming PROM: programmable sum of products with predefined products December 2018 Electronics for physicists Marc Weber - KIT 3

PROM December 2018 Electronics for physicists Marc Weber - KIT 4

PROM after programming December 2018 Electronics for physicists Marc Weber - KIT 5

December 2018 Electronics for physicists Marc Weber - KIT 6

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 Marc Weber - KIT 7

Complex PLDs (CPLD) • Programmable SPLDs • Programmable interconnects • Some CPLDs keep memory settings after power-off Structure of a CPLD Zoom in December 2018 Electronics for physicists Marc Weber - KIT 8

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 Marc Weber - KIT 9

FPGA building blocks • Logic cells: • Interconnects: MUX, flipflops, SRAM 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 several Terabit/s ! • „Soft“ or „hard“ micro processors • ADC for monitoring operation temperature and voltages • … December 2018 Electronics for physicists Marc Weber - KIT 10

Look-up table (LUT) Logic gates = Truth table = Look-up Table December 2018 Electronics for physicists Marc Weber - KIT 11

Illustration of a slice with two logic cells December 2018 Electronics for physicists Marc Weber - KIT 12

Logic block (CLB) December 2018 Electronics for physicists Marc Weber - KIT 13

A logic cell in operation December 2018 Electronics for physicists Marc Weber - KIT 14

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 Marc Weber - KIT 15

Illustration of interconnect logic Note the differences between • programmable input connection blocks and routing switches • long and short connections December 2018 Electronics for physicists Marc Weber - KIT 16

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 mm 2 area. December 2018 Electronics for physicists Marc Weber - KIT 17

Gate arrays (GAL) • Prefabricated set of transistors and logic gates Basic cells Double column array • Custom metal layers • Gate arrays offer low-density circuits at reduced costs December 2018 Electronics for physicists Marc Weber - KIT 18

FPGA design flow 1. Functional design in VHDL. Then functional (RTL) simulation 2. Synthesis: interpretation of VHDL code and mapping to FPGA building blocks (LUTs, MUX, registers, …. ) => Netlist. Then timing analysis 3. Implementation: Translate, map, place & route => bitstream 4. FPGA configuration: download bit stream into FPGA and run! December 2018 Electronics for physicists Marc Weber - KIT 19

ML 605 development board December 2018 Electronics for physicists Marc Weber - KIT 20

Virtex-6 Pinout (FF 1155 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 Marc Weber - KIT 21

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 Marc Weber - KIT 22

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 Marc Weber - KIT 23

Comparison FPGA & GPU &CPU December 2018 Electronics for physicists Marc Weber - KIT 24