Design and Development of Programmable Logic Hardware
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Design Entry Phase
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Today we're going to discuss the design entry phase of programmable logic hardware. In this phase, we use high-level hardware description languages like VHDL or Verilog. Does anyone know why we prefer HDLs over traditional schematic capture?
I think it's because HDLs can handle more complex designs?
Exactly! As designs become more complex, language-based tools allow for better management and description of hardware. Remember the acronym *VHDL* stands for 'VHSIC Hardware Description Language.'
What is VHSIC?
Good question! It stands for 'Very High-Speed Integrated Circuit.' Now, after writing our HDL code, what do we do next?
We need to simulate the design, right?
Yes! It's crucial to run functional simulations to ensure the design behaves as expected. Let's summarize today’s key points: using HDLs for complex designs and performing functional simulation afterward.
Hardware Compilation
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Now, let’s dive into hardware compilation. Can anyone tell me what happens during this step?
It involves synthesis and place-and-route.
Correct! First, we synthesize our HDL code. This produces a netlist. Does anyone know what a netlist is?
It’s a hardware representation that's device-independent?
Absolutely! The netlist describes how logical structures map without tying them to any specific device. Next is the place-and-route task. Student_2, could you explain that?
It maps the netlist onto actual logic blocks and interconnects.
Exactly! This step is what produces the bitstream used for programming the hardware. Let’s summarize: we create a device-independent netlist and then map it to logic blocks.
Key Differences in Design Thinking
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Important to note, there is a significant difference in thinking between hardware and software design. Can anyone identify this difference?
Hardware design involves parallel processing, while software is typically sequential?
That's right! In hardware, all input signals are processed simultaneously. When you write HDL, the structures you define are executed in parallel. This is fundamentally different from programming where steps execute one after another.
Does that mean we have to think about timing signals too?
Exactly! Timing control is vital in hardware design to ensure synchronization. Remember: *Parallel, Process, and Synchronize* are key elements in hardware design thinking. Summarizing today’s lesson: Parallel processing, timing control, and HDL are all critical to effective hardware design.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The design and development of programmable logic hardware involves several stages, including design entry through high-level hardware description languages, simulation of the design, and final synthesis into a format usable for programming the hardware. Key differences in thinking between hardware and software design are emphasized.
Detailed
Design and Development of Programmable Logic Hardware
This section discusses the comprehensive design and development process for programmable logic hardware, broken down into a sequence of steps depicted in a block diagram (Figure 9.34). The first stage involves design entry, where hardware is described using high-level hardware description languages (HDLs) like VHDL or Verilog, replacing traditional schematic capture methods due to increasing complexity in designs.
Following design entry, periodic functional simulation is performed to ensure the logic works correctly with a set of inputs, assuring functional correctness. The next phase is hardware compilation, which includes synthesis and place-and-route steps.
Synthesis generates a hardware representation called a netlist, independent of the specific programmable logic device (PLD). This netlist is crucial as it describes how the logical structure maps to physical hardware without being tied to a particular device's parameters. Place and Route maps the netlist onto the actual logic blocks, interconnects, and I/O, producing a bitstream that can be downloaded to the CPLD or FPGA for programming.
Thus, the design process emphasizes the parallel nature of hardware systems and the intricate synthesis processes that distinguish hardware from software development.
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Overview of the Design Process
Chapter 1 of 6
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Chapter Content
In this section, we will briefly discuss the various steps involved in the design and development of programmable logic hardware. Figure 9.34 shows a block diagram representation of the sequence of steps involved, in the order in which they are executed.
Detailed Explanation
This chunk introduces the topic of the design and development of programmable logic hardware, setting the stage for a detailed breakdown of the steps involved in the process. The mention of Figure 9.34 indicates that there is a visual representation of these steps, which helps in understanding how these steps are interlinked.
Examples & Analogies
Think of designing programmable logic hardware like planning a big event. You first clarify the event's concept (the initial design), then create a detailed itinerary (the source code), followed by confirming everything works together smoothly with a rehearsal (simulation) before the actual event.
Design Entry
Chapter 2 of 6
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Chapter Content
The process begins with a description of behavioural aspects and the architecture of the intended hardware. This is done by writing a source code in a high-level hardware description language (HDL) such as VHDL or Verilog. This step is known as design entry. Although schematic capture is also an option for design entry, it has been replaced with language-based tools owing to the designs becoming more and more complex, and also owing to advances in language-based tools.
Detailed Explanation
Design entry is the first critical step where the designer translates the requirements of the logic hardware into a formal representation using hardware description languages (HDLs). Languages like VHDL and Verilog allow for complex designs to be easily represented and modified. This step replaces older methods like schematic capture, making it easier to manage the complexities of modern designs.
Examples & Analogies
Imagine you are creating a recipe. Writing in an HDL is like detailing your recipe with specific ingredients and steps instead of just drawing pictures of the dishes. It makes it easier for someone else to cook the same meal later.
Simulation and Verification
Chapter 3 of 6
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Chapter Content
The design entry step is either followed by or interspersed with periodic functional simulation. The simulator executes the design for a given set of inputs and confirms that the logic is functionally correct.
Detailed Explanation
Once the design entry is complete, simulation is run to test the logic of the design. This simulation checks whether the design behaves as expected with the specified inputs, helping to identify any issues early in the design process. It's an essential validation step before moving to the next phase.
Examples & Analogies
Think of simulation like a test run for a car. Before the car goes out on the road, you would want to drive it around the parking lot to make sure everything works correctly and that it responds as expected.
Hardware Compilation
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Chapter Content
Hardware compilation comes next. It involves two steps. The first step is synthesis, and the result of that is a hardware representation called a netlist. The netlist is device-independent and its contents do not depend on the parameters of the PLD to be programmed.
Detailed Explanation
Hardware compilation involves translating the HDL code into a netlist, which is a list defining the components and how they connect in the hardware. This netlist serves as a blueprint for the next steps, and since it's device-independent, it can be used with various programmable logic devices (PLDs).
Examples & Analogies
Creating a netlist is like making a blueprint for a house after you’ve sketched your design. The blueprint outlines what materials are needed and how everything should fit together, regardless of where the house will be built.
Place and Route
Chapter 5 of 6
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Chapter Content
The second step, called place and route, involves mapping of the logical structure described in the netlist onto actual logic blocks, interconnects, and inputs/outputs. The place and route process produces a bitstream, which is nothing but the binary data that must be loaded into CPLD/FPGA to make the chip execute the intended hardware design.
Detailed Explanation
Place and route is the process that physically organizes the design on the PLD. This step decides where each element will be placed and how they will interconnect. The outcome is a bitstream, a binary file used to program the PLD to realize the designed functionality.
Examples & Analogies
Think of place and route like setting up furniture in a house. After you have a blueprint, you then decide exactly where each piece of furniture will go and how they’re connected (like walking space between chairs) before you finally create a comfortable living space.
Downloading the Bitstream
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Chapter Content
It may be mentioned here that each device family has its own proprietary bitstream format.
Detailed Explanation
Finally, the generated bitstream is downloaded onto the PLD. This step makes the design functional in hardware. However, it's important to note that each family of devices (like CPLDs or FPGAs) has its specific format for the bitstream, which ensures compatibility and correct operation.
Examples & Analogies
Downloading the bitstream is akin to installing software on your computer. Each software must be compatible with your computer's operating system, just like the bitstream must match the device's format to work properly.
Key Concepts
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Design Entry: Using HDLs to describe hardware components and functions.
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Simulation: Testing the designed logic for correctness before synthesis.
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Synthesis: Producing a device-independent netlist from an HDL.
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Place-and-Route: Mapping the netlist onto real hardware structures.
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Bitstream: The final output to configure a programmable device.
Examples & Applications
Example of using VHDL for describing a simple logic gate or flip-flop.
Illustration of the bitstream that would be downloaded to a CPLD after synthesis.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
In parallel signals flow, through each block they go; HDL's the way to start, then simulate with heart!
Stories
Imagine a conductor leading a symphony where each musician plays their part at once - that's how a hardware design works in parallel, guided by the composer, the HDL.
Memory Tools
Remember 'SIMPLE' for the synthesis process: Synthesis, Independent netlist, Mapping, Place-and-Route, Logic blocks, and Execution.
Acronyms
HDL
High-level Design for Logic.
Flash Cards
Glossary
- HDL
Hardware Description Language, a specialized computer language used to describe the behavior and structure of electronic circuits.
- Netlist
A device-independent representation of a design's components and their connections.
- Synthesis
The process of converting HDL code into a netlist.
- PlaceandRoute
The process of mapping a netlist onto actual logic blocks and interconnects within a programmable device.
- Bitstream
A binary data format that configures programmable logic devices to execute a specific hardware design.
Reference links
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