A complex programmable logic device (CPLD) is a programmable logic device

Programmable logic device

A programmable logic device or PLD is an electronic component used to build reconfigurable digital circuits. Unlike a logic gate, which has a fixed function, a PLD has an undefined function at the time of manufacture...

 with complexity between that of PAL

Programmable Array Logic

The term Programmable Array Logic is used to describe a family of programmable logic device semiconductors used to implement logic functions in digital circuits introduced by Monolithic Memories, Inc. in March 1978. MMI obtained a registered trademark on the term PAL for use in "Programmable...

s and FPGA

Field-programmable gate array

A field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...

s, and architectural features of both. The building block of a CPLD is the macrocell

Macrocell array

A macrocell array is an approach to the design and manufacture of ASICs. Essentially, it is a small step up from the otherwise similar gate array, but rather than being a prefabricated array of simple logic gates, the macrocell array is a prefabricated array of higher-level logic functions such as...

, which contains logic implementing disjunctive normal form

Disjunctive normal form

In boolean logic, a disjunctive normal form is a standardization of a logical formula which is a disjunction of conjunctive clauses. As a normal form, it is useful in automated theorem proving. A logical formula is considered to be in DNF if and only if it is a disjunction of one or more...

 expressions and more specialized logic operations.

Features in common with PAL

Programmable Array Logic

The term Programmable Array Logic is used to describe a family of programmable logic device semiconductors used to implement logic functions in digital circuits introduced by Monolithic Memories, Inc. in March 1978. MMI obtained a registered trademark on the term PAL for use in "Programmable...

s:

• Non-volatile configuration memory. Unlike many FPGAs, an external configuration ROM
  Read-only memory
  Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
  
   isn't required, and the CPLD can function immediately on system start-up.
• For many legacy CPLD devices, routing constrains most logic blocks to have input and output signals connected to external pins, reducing opportunities for internal state storage and deeply layered logic. This is usually not a factor for larger CPLDs and newer CPLD product families.

Features in common with FPGAs:

• Large number of gates available. CPLDs typically have the equivalent of thousands to tens of thousands of logic gate
  Logic gate
  A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...
  
  s, allowing implementation of moderately complicated data processing devices. PALs typically have a few hundred gate equivalents at most, while FPGAs typically range from tens of thousands to several million.
• Some provisions for logic more flexible than sum-of-product
  Disjunctive normal form
  In boolean logic, a disjunctive normal form is a standardization of a logical formula which is a disjunction of conjunctive clauses. As a normal form, it is useful in automated theorem proving. A logical formula is considered to be in DNF if and only if it is a disjunction of one or more...
  
   expressions, including complicated feedback paths between macro cells, and specialized logic for implementing various commonly-used functions, such as integer
  Integer
  The integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...
  
   arithmetic
  Arithmetic
  Arithmetic or arithmetics is the oldest and most elementary branch of mathematics, used by almost everyone, for tasks ranging from simple day-to-day counting to advanced science and business calculations. It involves the study of quantity, especially as the result of combining numbers...
  
  .

The most noticeable difference between a large CPLD and a small FPGA is the presence of on-chip non-volatile memory in the CPLD. This distinction is rapidly becoming less relevant, as several of the latest FPGA products also offer models with embedded configuration memory.

The characteristic of non-volatility makes the CPLD the device of choice in modern digital designs to perform 'boot loader' functions before handing over control to other devices not having this capability. A good example is where a CPLD is used to load configuration data for an FPGA from non-volatile memory.

CPLDs were an evolutionary step from even smaller devices that preceded them, PLA

Programmable logic array

A programmable logic array is a kind of programmable logic device used to implement combinational logic circuits. The PLA has a set of programmable AND gate planes, which link to a set of programmable OR gate planes, which can then be conditionally complemented to produce an output...

s (first shipped by Signetics

Signetics

Signetics, once a major player in semiconductor manufacturing, made a variety of devices which included integrated circuits, bipolar and MOS, the Dolby circuit, logic, memory and analog circuits. They developed microprocessors like the 2650, the bipolar 8X300 and had licensed Motorola 68000...

), and PAL

Programmable Array Logic

The term Programmable Array Logic is used to describe a family of programmable logic device semiconductors used to implement logic functions in digital circuits introduced by Monolithic Memories, Inc. in March 1978. MMI obtained a registered trademark on the term PAL for use in "Programmable...

s. These in turn were preceded by standard logic

Logic family

In computer engineering, a logic family may refer to one of two related concepts. A logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, usually with compatible logic levels and power supply...

 products, that offered no programmability and were "programmed" by wiring several standard logic chips together.

The main distinction between FPGA and CPLD device architectures is that FPGAs are internally based on Look-up tables

Lookup table

In computer science, a lookup table is a data structure, usually an array or associative array, often used to replace a runtime computation with a simpler array indexing operation. The savings in terms of processing time can be significant, since retrieving a value from memory is often faster than...

 (LUTs) while CPLDs form the logic functions with sea-of-gates (e.g. sum of products).

See also

• Application-specific integrated circuit
  Application-specific integrated circuit
  An application-specific integrated circuit is an integrated circuit customized for a particular use, rather than intended for general-purpose use. For example, a chip designed solely to run a cell phone is an ASIC...
  
   (ASIC)
• Erasable programmable logic device (EPLD)
• Simple programmable logic device
  Simple programmable logic device
  A simple programmable logic device is a programmable logic device with complexity below that of a complex programmable logic device .The term commonly refers to devices such as ROMs, PALs, PLAs and GALs....
  
   (SPLD)
• Macrocell array
  Macrocell array
  A macrocell array is an approach to the design and manufacture of ASICs. Essentially, it is a small step up from the otherwise similar gate array, but rather than being a prefabricated array of simple logic gates, the macrocell array is a prefabricated array of higher-level logic functions such as...
  
  
• Programmable array logic
  Programmable Array Logic
  The term Programmable Array Logic is used to describe a family of programmable logic device semiconductors used to implement logic functions in digital circuits introduced by Monolithic Memories, Inc. in March 1978. MMI obtained a registered trademark on the term PAL for use in "Programmable...
  
   (PAL)
• Programmable logic array
  Programmable logic array
  A programmable logic array is a kind of programmable logic device used to implement combinational logic circuits. The PLA has a set of programmable AND gate planes, which link to a set of programmable OR gate planes, which can then be conditionally complemented to produce an output...
  
   (PLA)
• Programmable logic device
  Programmable logic device
  A programmable logic device or PLD is an electronic component used to build reconfigurable digital circuits. Unlike a logic gate, which has a fixed function, a PLD has an undefined function at the time of manufacture...
  
   (PLD)
• Field-programmable gate array
  Field-programmable gate array
  A field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...
  
   (FPGA)
• VHSIC Hardware Description Language
  VHSIC Hardware Description Language
  VHDL is a hardware description language used in electronic design automation to describe digital and mixed-signal systems such as field-programmable gate arrays and integrated circuits.- History :...
  
   (VHDL)
• Verilog Hardware Description Language
  Verilog
  In the semiconductor and electronic design industry, Verilog is a hardware description language used to model electronic systems. Verilog HDL, not to be confused with VHDL , is most commonly used in the design, verification, and implementation of digital logic chips at the register-transfer level...
  
  

Some notable CPLD suppliers

• Altera
  Altera
  Altera Corporation is a Silicon Valley manufacturer of PLDs . The company offered its first programmable logic device in 1984. PLDs can be reprogrammed during the design cycle as well as in the field to perform multiple functions, and they support a fairly fast design process...
  
  
• Atmel
  Atmel
  Atmel Corporation is a manufacturer of semiconductors, founded in 1984. Its focus is on system-level solutions built around flash microcontrollers...
  
  
• Cypress Semiconductor
  Cypress Semiconductor
  Cypress Semiconductor Corporation is a Silicon Valley-based semiconductor design and manufacturing company founded by T. J. Rodgers and others from Advanced Micro Devices. It was formed in 1982 with backing by Sevin Rosen and went public in 1986. The company initially focused on the design and...
  
  
• Lattice Semiconductor
  Lattice Semiconductor
  Lattice Semiconductor Corporation is a United States based manufacturer of high-performance programmable logic devices . Founded in 1983, the company employs about 700 people and has annual revenues of around $300 million, with Darin Billerbeck as the chief executive officer...
  
  
• Xilinx
  Xilinx
  Xilinx, Inc. is a supplier of programmable logic devices. It is known for inventing the field programmable gate array and as the first semiconductor company with a fabless manufacturing model....