What does CPLD mean?

Integrated circuits (ICs) known as Complex Programmable Logic Devices (CPLDs) can be utilized in place of circuits built from several logic ICs. Unlike discrete logic IC circuits, the logic in a CPLD can be changed repeatedly without requiring a PCB update.

A programmable interconnect matrix cell surrounded by programmable logic macrocells (MC) is the core element of a CPLD (Complex Programmable Logic Device). The MC structure stands out as being the most sophisticated among them and having a complex I/O cell interconnection structure that may be built by the user based on the demands of a specific circuit structure to perform certain jobs. The CPLD uses fixed-length metal wires for the internal connections of each logic block, eliminating the problem that the timing of the segmented interconnection structure is not completely predictable. As a result, the produced logic circuits are time-predictable.

History of CPLD

In the 1970s, the PLD, the first programmable logic device, was developed. PLDs are programmable logic devices (PLDs), which are integrated circuits (ICs) containing a lot of flip-flops and logic gates. An array of AND and OR gates makes up the most basic programmable logic device, and both the array's logic and the connections between the gates may be programmed. Three general categories can be used to classify PLDs. Field programmable gate arrays (FPGA), SPLDs, and CPLDs are three types of programmable logic devices.

Since it could be completed by software, the design of its hardware structure was far more adaptable than that of pure hardware digital circuits. However, they could only be used to design small-scale circuits because of their very simplistic architecture. Complex programmable logic devices, or CPLDs, were first introduced in the middle of the 1980s to overcome the constraint that PLDs can only build small-scale circuits.

CPLD Features

1. CPLD has a wide range of applications, flexible programming, high integration, a short design and development cycle, and better development tools.
2. CPLD also offers benefits like inexpensive design and production costs, low hardware experience requirements for designers, no testing required for standard goods, high confidentiality, and a widely acceptable price, among others.
3. Because it can implement larger-scale circuit design, CPLD is commonly utilized in product prototypes and product manufacture (usually below 10,000 pieces).
4. A programmable AND/OR array and macrocells make up a CPLD's internal structure.
5. Memory that isn't lost: The logic design that has been loaded into the CPLD will not be lost if the power is switched off. The logic circuit will be prepared after the CPLD's power is turned on.

PLD vs. CPLD

Due to their extremely simplistic construction, they could only be utilized to implement tiny circuits. PLDs can only create small-scale circuits, therefore complex programmable logic devices, or CPLDs, were initially proposed in the middle of the 1980s to address this limitation.
PLDs offer more performance and versatility due to their replaceable hardware. Along with SPLDs and FPGAs, CPLDs are one of the three major subcategories of PLDs. CPLDs have performance and complexity that are in the middle between SPLDs and FPGAs.

CPLD vs. FPGA

Small- to medium-sized applications are better suited for CPLD than complex ones are for FPGA. In addition, CPLDs are superior to FPGAs at predicting delays. The CPLD is more secure than the FPGA because of its nonvolatile internal memory. Unlike FPGA, which is an integrated circuit intended to be updated by a client or a designer after manufacture, CPLD is an integrated circuit that supports the construction of digital systems.

Another key distinction between CPLD and FPGA is the logic resource. FPGA gives a huge amount of logic resources and storage components to create complicated systems, whereas CPLD delivers the bare minimum. Electricity consumption by CPLD and FPGA differs; CPLD uses less power than FPGA, which uses more. The FPGA is more expensive than CPLDs, but CPLDs are more cost-effective.

CPLD Applications

Consider using a CPLD when a design calls for the utilization of numerous 7400 series logic ICs. A CPLD will be more inexpensive, faster, and programmable with the right pin-out configuration for simpler PCBs. Use CPLDs when producing intricate designs that may require several iterations. It is more challenging to design, etch, and stuff a new circuit board than it is to create a new circuit in software and upload it to the CPLD.

Select a CPLD if you want maximum speed and prompt reaction. Amazingly, microcontrollers only respond to interrupts at a few MHz whereas CPLDs start at 100MHz. When an external stimulus is applied, CPLD designs create circuits that respond almost instantly. Even interrupt procedures have a somewhat large latency when a microcontroller executes code to respond to events.

How to program CPLD?

VHDL is a hardware description language (HDL) that can be used to describe a logic design. When software tools scan a VHDL logic design, they produce a configuration file that can be loaded into an FPGA or CPLD to implement the logic design there. VHDL is the abbreviation for VHSIC Hardware Description Language. This is referred to as a Very High-Speed Integrated Circuit.

The Institute of Electrical and Electronics Engineers (IEEE) has standardized the vendor-neutral language VHDL. It can now be used again and transported. Most statements in VHDL occur continuously (in parallel with one another), not sequentially, in contrast to traditional computer programs. Another standardized and vendor-neutral HDL option to VHDL is Verilog.