This makes fpgas very nice for use in prototyping

This preview shows page 63 - 71 out of 103 pages.

This makes FPGAs very nice for use in prototyping ASICs, or in places where and ASIC will eventually be used. FPGA has narrower logic choices and more memory elements. LUT (Lookup Table) may replace actual logic gates. Design turnaround time is only a few hours 63
Image of page 63

Subscribe to view the full document.

Lookup Table A LUT (Lookup table) is a one bit wide memory array A 4-input AND gate is replaced by a LUT that has four address inputs and one single bit output with 16 one bit locations Location 15 would have a logic value ‘1’ stored, all others would be zero LUT’s can be programmed and reprogrammed to change the logical function implemented 64
Image of page 64
Field Programmable Gate Arrays An FPGA is usually just larger and more complex than a PLD None of the mask layers are customized A method for programming the basic logic cells and the interconnect Array of programmable basic logic cells that can implement Combinational and Sequential logic 65
Image of page 65

Subscribe to view the full document.

66 FPGA - Generic Structure FPGA building blocks: Programmable logic blocks Implement combinatorial and sequential logic Programmable interconnect Wires to connect inputs and outputs to logic blocks Programmable I/O blocks Special logic blocks at the periphery of device for external connections I/O I/O Logic block Interconnection switches I/O I/O
Image of page 66
FPGA Architecture The architecture consists of Configurable Logic blocks Configurable I/O blocks Programmable interconnect. Clock circuitry for driving the clock signals to each logic block, Additional logic resources such as ALUs, memory, and decoders may be available. The two basic types of programmable elements for an FPGA are Static RAM and anti-fuses. 67
Image of page 67

Subscribe to view the full document.

Programming types in FPGA SRAM Programming It involves small Static RAM bits for each programming element. Writing the bit with a zero turns off a switch, while writing with a one turns on a switch. Anti-fuse Programming It consist of microscopic fuses which, unlike a regular fuse, normally makes no connection. A certain amount of current during programming of the device causes the two sides of the fuse to connect. 68
Image of page 68
Basic FPGA Operation Write Configuration Memory Defines system function Input/Output Cells Logic in Cells Connections between Logic cells & I/O cells Changing configuration memory data => changes system function Configuration can change at anytime Even while system function is in operation Run-time reconfiguration ( RTR ) 69
Image of page 69

Subscribe to view the full document.

70 Advantages of FPGA Faster time-to-market - no layout, masks or other manufacturing steps are needed No upfront NRE (non recurring expenses) - costs typically associated with an ASIC design Simpler design cycle - due to software that handles much of the routing, placement, and timing More predictable project cycle - due to elimination of potential re-spins, wafer capacities, etc.
Image of page 70
Image of page 71
  • Fall '15
  • Gate, Integrated Circuit, Programmable logic device, Field-programmable gate array, PLA, Application-specific integrated circuit, gate array

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern