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Electronics for Physicists
Lecture 16 Programmable Logic
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Programmable Digital Logic
+ FPGA December 2017 Electronics for physicists
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PROM PROM: programmable sum of products with predefined products
PROM before programming PROM: programmable sum of products with predefined products December 2017 Electronics for physicists
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Electronics for physicists
PROM December 2017 Electronics for physicists
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PROM PROM after programming December 2017 Electronics for physicists
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Electronics for physicists
December 2017 Electronics for physicists
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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 2017 Electronics for physicists
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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 2017 Electronics for physicists
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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 2017 Electronics for physicists
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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 – 28 Gb/s lines) „Soft“ or „hard“ micro processors ADC for monitoring operation temperature and voltages … December 2017 Electronics for physicists
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Logic gates = Truth table = Look-up Table
Look-up table (LUT) Logic gates = Truth table = Look-up Table December 2017 Electronics for physicists
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Illustration of a slice with two logic cells
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Electronics for physicists
Logic block (CLB) December 2017 Electronics for physicists
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A logic cell in operation
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Electronics for physicists
Example: SLICEL Note that: LUT outputs can be connected there are different type of MUXs the carry structure to connect different slices December 2017 Electronics for physicists
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Illustration of interconnect logic
Note the differences between programmable input connection blocks and routing switches long and short connections December 2017 Electronics for physicists
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Electronics for physicists
ASIC costs Integrated circuit tier structure 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. December 2017 Electronics for physicists
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Electronics for physicists
Gate arrays (GAL) Prefabricated set of transistors and logic gates Custom metal layers Gate arrays often low-density circuits at reduced costs Basic cells Double column array December 2017 Electronics for physicists
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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 2017 Electronics for physicists
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Electronics for physicists
ML605 development board December 2017 Electronics for physicists
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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 2017 Electronics for physicists
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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 2017 Electronics for physicists
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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 2017 Electronics for physicists
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Comparison FPGA & GPU &CPU
December 2017 Electronics for physicists
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