Sequential Programmable Devices Sequential Programmable Devices The combinational

Sequential Programmable Devices

Sequential Programmable Devices • The combinational PLD consist only gates • Sequential Programmable Devices includes both gates and filp-flop • Type of sequential Programmable Devices: – Sequential (simple) programmable logic device (SPLD) – Complex programmable logic device (CPLD) – Field programmable gate array (FPGA)

SPLD • SPLD: consist PAL and D flip-flop • Each section in SPLD is called Microcell

SPLD • The basic microcell logic – AND-OR array – Edge-triggered D flip-flop – Three-state buffer(inverter) • A typical SPLD has from 8 to 10 macrocells within one IC package

CPLD • CPLD is a collection of individual PLDs on a single integrated circuit • Each PLD typically contains from 8 to 16 macroce. Ils • CPLD has two levels of programmability: – Each PLD block – Interconnections between the PLDs • Each I/0 pin is driven by a three state buffer and can be programmed to act as input or output

FPGA • FPGA is a VLSI circuit that can be programmed at the user's location • Consist of: – hundreds or thousands of logic blocks – Programmable interconnection – programmable input and output blocks

Logic block • Used to implement any boolean function • Consist of: – Look up table (LUTs) , Multiplexers , PLD blocks or NAND gates (implemented logic function) – Multiplexers (select 1 of N inputs) – Flip-flop, Registers. Clocked Storage elements.

Interconnection (Routing) • FPGAs have 3 programmable routing resources : – Vertical and horizontal routing channels – Connection boxes • connect input and output pins of the CLBs to wires of the vertical or the horizontal routing channels – Switch boxes • connect wire segments in the horizontal and vertical channels • Technology of connection – – Static RAM Anti fuse EPROM EEPROM

I/O blocks • They allow the pins of the FPGA chip to function either as input pins, output pins or input/output pins Programmable I/O

Circuit compilation

Major FPGA Vendors • SRAM-based FPGAs – Xilinx, Inc. – Altera Corp. – Atmel – Lattice Semiconductor • Flash & antifuse FPGAs – Actel Corp. – Quick Logic Corp.

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