Introduction to Embedded - CPLDs (Complex Programmable Logic Devices)

Introduction to Embedded - CPLDs (Complex Programmable Logic Devices) 

CPLD (Complex Programmable Logic Device) is the abbreviation of Complex PLD, a logic element that is more complex than PLD. CPLD is a digital integrated circuit in which users can construct logic functions according to their own needs. The basic design method is to use the integrated development software platform to generate corresponding target files by means of schematic diagrams and hardware description languages, and transmit the code to the target chip through the download cable ("in-system" programming) to realize the designed digital system.

Here's an introduction to embedded CPLDs:

1.Programmability: CPLDs are programmable devices, meaning that their functionality can be customized by the designer. They are typically programmed using a hardware description language (HDL) such as VHDL or Verilog. The HDL code describes the desired logic functions, which is then synthesized and transformed into a configuration file or bitstream that programs the CPLD. This programmability allows for rapid prototyping, iterative design, and flexibility in implementing custom logic.

2.Logic Capacity: CPLDs have a medium-scale logic capacity, which means they can implement moderate-sized digital logic designs. They typically consist of multiple programmable logic blocks (PLBs) that contain look-up tables (LUTs) and flip-flops. The number of PLBs and the capacity of LUTs determine the overall logic capacity of the CPLD. While CPLDs have a smaller logic capacity compared to FPGAs, they are well-suited for applications that require moderate complexity.

3.Interconnect Flexibility: CPLDs offer flexible programmable interconnects that allow designers to connect the logic blocks and route signals as needed. The interconnect resources, such as routing channels and switches, can be configured to establish connections between the inputs and outputs of the logic blocks. This flexibility enables the designer to create custom logic designs with specific interconnections, enabling efficient implementation of complex digital systems.

4.Deterministic Timing: CPLDs provide deterministic timing characteristics, meaning that the propagation delay through the logic blocks and interconnects is predictable and consistent. This deterministic behavior is beneficial for applications that require precise timing control, such as synchronous digital systems or real-time applications. CPLDs can provide fast response times due to their fixed interconnect structures, making them suitable for time-critical applications.

5.I/O Flexibility: CPLDs offer a range of input/output (I/O) options to interface with external devices and peripherals. The I/O pins can be configured to support various voltage standards, such as LVCMOS, LVTTL, or specialized I/O standards. CPLDs can be used for general-purpose I/O, as well as specific functions like serial communication (UART, SPI, I2C), memory interfaces, or other specialized protocols. The I/O flexibility enables seamless integration of the CPLD with other components in the embedded system.

6.Low Power Consumption: CPLDs typically consume lower power compared to FPGAs due to their smaller size and simplified architecture. They are designed to optimize power consumption by dynamically disabling unused logic blocks and providing power management features. This makes CPLDs suitable for power-sensitive embedded applications, battery-powered devices, or applications with strict power constraints.

7.Package Types: CPLDs are available in various package types, such as QFP (Quad Flat Pack), BGA (Ball Grid Array), or TQFP (Thin Quad Flat Pack). The package type determines the physical dimensions, pin count, and mounting options of the CPLD on a printed circuit board (PCB). The choice of package type depends on factors such as board space limitations, thermal considerations, and manufacturing requirements.

Embedded CPLDs find applications in a wide range of industries, including industrial automation, telecommunications, automotive electronics, consumer electronics, and more. They provide a flexible and cost-effective solution for implementing custom digital logic designs in embedded systems, enabling designers to achieve optimized functionality, improved performance, and faster time-to-market.

Physical Characteristics of Embedded - CPLDs (Complex Programmable Logic Devices)

The physical characteristics of embedded CPLDs refer to the physical attributes and considerations associated with these devices. Here are some common physical characteristics of embedded CPLDs:

1.Package Types: CPLDs come in various package types, such as QFP (Quad Flat Pack), BGA (Ball Grid Array), TQFP (Thin Quad Flat Pack), or others. The package type determines the physical dimensions, pin count, and mounting options of the CPLD on a printed circuit board (PCB). The choice of package type depends on factors such as board space limitations, thermal considerations, and manufacturing requirements.

2.Pin Count: The pin count of an embedded CPLD defines the number of external connections available on the device. The pin count varies based on the specific CPLD model and package type. Designers need to consider the required number of I/O pins and any specific pin configurations needed for interfacing with other components in the embedded system.

3.Pin Configuration: The pin configuration of an embedded CPLD refers to the arrangement and assignment of I/O pins and other control pins on the device. The pin configuration determines how the CPLD connects to external devices and interfaces. Designers must carefully consider the pin configuration to ensure proper connectivity and compatibility with the rest of the system.

4.Power Supply: Embedded CPLDs require a stable and regulated power supply for their operation. The power supply voltage and current requirements are specified by the CPLD manufacturer and must be adhered to for reliable and correct functionality. Designers need to ensure appropriate power supply routing, decoupling capacitors, and power integrity considerations to provide clean and stable power to the CPLD.

5.Operating Temperature Range: CPLDs have specific operating temperature ranges within which they can function reliably. The operating temperature range is typically provided by the manufacturer and should be considered during system design and enclosure selection. Exceeding the specified temperature range can lead to performance degradation or even device failure.

6.Mounting and Assembly: Embedded CPLDs are mounted on PCBs using standard assembly techniques. Designers need to follow best practices for component placement, soldering, and assembly processes to ensure reliable connections and proper thermal management. The PCB layout should consider the CPLD's pinout, signal integrity requirements, and thermal considerations.

7.Environmental Considerations: Embedded CPLDs may be subjected to various environmental conditions, such as humidity, vibration, shock, or electromagnetic interference (EMI). Designers should consider environmental factors during the system design and ensure proper protection and shielding mechanisms to mitigate the impact of these conditions on the CPLD's performance and reliability.

8.ESD Protection: Electrostatic discharge (ESD) protection is important for embedded CPLDs, as they can be sensitive to electrostatic discharge during handling or operation. Designers need to incorporate proper ESD protection measures, such as ESD diodes or grounding techniques, to prevent ESD damage and ensure the long-term reliability of the CPLD.

These physical characteristics are essential considerations when integrating CPLDs into an embedded system. By carefully addressing these aspects, designers can ensure proper functionality, reliable operation, and effective integration of the CPLD within the overall system.

Electrical Characteristics of Embedded - CPLDs (Complex Programmable Logic Devices)

The electrical characteristics of embedded CPLDs refer to the electrical properties and specifications that define their operation and interaction with the surrounding circuitry. Here are some common electrical characteristics of embedded CPLDs:

1.Supply Voltage: Embedded CPLDs require a specific supply voltage for proper operation. The supply voltage is typically specified by the CPLD manufacturer and must be provided within the specified range to ensure correct functionality. Designers should ensure that the power supply voltage is stable and regulated to prevent voltage fluctuations that can adversely affect CPLD operation.

2.Power Consumption: CPLDs have power consumption characteristics that define the amount of power they require during operation. The power consumption of a CPLD is influenced by factors such as the logic design implemented, switching frequency, and operational modes. Designers need to consider the power consumption of the CPLD and ensure that the power supply can meet the required current demands.

3.I/O Voltage Levels: Embedded CPLDs support different I/O voltage standards, such as LVCMOS (Low-Voltage CMOS) or LVTTL (Low-Voltage TTL). These voltage levels determine the logic high and logic low thresholds for the I/O pins. Designers must ensure that the I/O voltage levels of the CPLD are compatible with the voltage levels of the devices it interfaces with, such as microcontrollers, memory modules, or other peripheral components.

4.I/O Standards and Interfaces: CPLDs support various I/O standards and interfaces, such as UART, SPI, I2C, or memory interfaces. Each standard has specific electrical characteristics and timing requirements. Designers should adhere to the electrical specifications of the chosen I/O standards when designing the CPLD-based system to ensure proper signal integrity, voltage levels, and timing compatibility.

5.Timing Constraints: CPLDs have specific timing characteristics, including input setup and hold times, clock-to-output delay, and other timing parameters. These timing constraints ensure proper operation and reliable data transfer within the CPLD. Designers need to consider these timing requirements when designing and implementing the logic circuitry to ensure correct data capture, propagation, and synchronization.

6.Current Sourcing and Sinking Capability: CPLDs have current sourcing and sinking capabilities for driving output signals and interfacing with external devices. The current limits of the CPLD's output pins define the maximum current that can be sourced or sunk by the pins. Designers need to consider the current requirements of the connected devices and ensure that the CPLD can provide sufficient current for reliable operation.

7.Noise Immunity: Embedded CPLDs should exhibit good noise immunity to withstand electrical noise and disturbances present in the system. This ensures reliable operation and minimizes the susceptibility of the CPLD to external noise sources. Designers should consider noise filtering techniques, proper grounding, and signal integrity measures to enhance the noise immunity of the CPLD-based system.

8.ESD Protection: Embedded CPLDs should have proper electrostatic discharge (ESD) protection to prevent damage from ESD events. ESD protection mechanisms, such as ESD diodes or transient voltage suppressors, are typically incorporated into the design to divert and absorb high voltage spikes caused by ESD events. Designers should ensure that the CPLD is adequately protected against ESD to prevent permanent damage.

These electrical characteristics are crucial for the proper operation and integration of embedded CPLDs into an overall system. Designers must consider these specifications and requirements to ensure compatibility, reliability, and optimal performance of the CPLD-based embedded system.

Embedded - CPLDs (Complex Programmable Logic Devices) development history and application fields

In the 1970s, the earliest programmable logic device - PLD was born. Its output structure is a programmable logic macro unit, because its hardware structure design can be completed by software (equivalent to manually designing a local indoor structure after the house is built), so its design is more flexible than pure hardware digital circuits , but its too simple structure also makes them only realize the circuit of smaller scale. In order to make up for the defect that PLD can only design small-scale circuits, in the mid-1980s, a complex programmable logic device-CPLD was introduced. At present, the application has penetrated into the network, instrumentation, automotive electronics, CNC machine tools, aerospace measurement and control equipment, etc.

How should Embedded - CPLDs (Complex Programmable Logic Devices) be used?

CPLD is a digital integrated circuit in which users can construct logic functions according to their own needs. The basic design method is to use the integrated development software platform to generate corresponding target files by means of schematic diagrams and hardware description languages, and transmit the code to the target chip through the download cable ("in-system" programming) to realize the designed digital system.

Identification and classification of FPGA and Embedded - CPLDs (Complex Programmable Logic Devices)

The identification and classification of FPGA and CPLD are mainly based on their structural characteristics and working principles. The usual classification methods are:

CPLDs are devices that form logical behavior in the form of a product term structure, such as Lattice's ispLSI series, Xilinx's XC9500 series, Altera's MAX7000S series, and Lattice (formerly Vantis) Mach series, etc.

A device that uses a look-up table structure to form logic behavior is called an FPGA, such as Xilinx's SPARTAN series, Altera's FLEX10K or ACEX1K series, etc.