CPLD Complex Programmable Logic Device Need of CPLD

CPLD (Complex Programmable Logic Device) • Need of CPLD : Due to limitations of SPLDs(PLA and PAL). It is Collection of PLDs and interconnection on same die. Logic gates upto 10000 gates. Vendors: Altera, Atmel, Cypress, Philips etc.

Structural Block Diagram of CPLD Programmablen I/O blocks PLD PLD Programmable Interconnect PLD PLD

Detail Architecture of CPLD

Functional Block

Macrocell

Macrocell: Consists: AND-OR configuration(5 -20 AND gates, OR gates with 5 -20 inputs). Ex-OR gate(provides inverted or noninverted output of ORgate). D-Flip-Flop. Multiplexer. Buffer.

Advantages of CPLD? • Ease of Design: With use of HDL & CPLD development tools • Reduced Board Area: As uses VLSI & available in tiny sizes. • Cost of Ownership: Due to less maintenance. • Lower Development Costs • More product revenue: Development cycles are very short & get into market quicker, generates revenue sooner. • Reliability

Field-Programmable Gate Arrays Introduced in 1985 by XILINX Company. Since then many different companies developed it: Actel, Altera, Algotronix, Quick Logic, AMD, Cross Point Solutions etc. PLAs: 100 s of gate equivalents FPGAs: 1000 -few hundred 1000 s gates Logic blocks(CLB) Implement combinational and sequential logic Interconnect Wires to connect inputs and outputs to logic blocks I/O blocks Special logic blocks at periphery of device for external connections

CLB(Configurable Logic Blocks) Number of ways defining CLB that it varies from simple AND gate to very complex structure consisting MUX or LUT & so many PLA kind structure.

FPGA LOGIC BLOCK 4 -input look up table (LUT) Implements combinational logic functions Register Optionally stores output of LUT

I/O pads configured as inputs Selectable 2. 5 V or 3. 3 V threshold levels Optional pull-up resistor I/O pads configured as outputs Ability to drive LVTTL and LVCMOS levels

Xilinx 4000 Interconnect

APPLICATIONS OF FPGA □Prototyping -Ensemble of gate arrays used to emulate a circuit to be manufactured -Get more/better/faster debugging done than with simulation □ Reconfigurable hardware -One hardware block used to implement more than one function □ Special-purpose computation engines -Hardware dedicated to solving one problem (or class of problems) -Accelerators attached to general-purpose computers (e. g. , in a cell phone!)

SEQUENTIAL PLD Output Logic Macrocell (OLM) combinational config product term invert output? registered config D F/F 16

Difference between CPLD & FPGA Sr. No. CPLD FPGA 1. Complex Programmable Logic Device Field Programmable Gate Array 2. It is collection PLDs. It is collection of CLBs. 2. Gate density up to 10000 gates 1000 -few hundred 1000 s gates 4. Interconnection wise it is complex so called as CPLD. Programmable at field or site so called as FPGA. 5. PAL like blocks used as PLDs. CLBs used as building blocks. 6. AND-OR arrays are there in PAL like blocks. LUTs are there in CLBs. 7. Configuration context is stored in ROM. Configuration context is stored in RAM. 8. Configuration context is Non- Configuration context is volatile.