Hardware/software codesign is the joint design and evaluation of an embedded system’s hardware, software, and the interfaces that connect them. Transaction-level modeling (TLM) makes that work practical by providing a shared way to explore a system at several levels of detail—from fast functional models to models with timing and cycle-level behavior—without treating architecture and implementation as separate handoffs.
What hardware/software codesign means
In a conventional handoff, an architect decides what the system should do and how it should be divided, then hardware and software developers implement those decisions separately. Codesign instead evaluates the system as a whole: its functions, hardware architecture, software, and communication between components. That makes it possible to ask not only whether a function works, but where it should run and how its placement affects the rest of the design.
Bassam Tabbara captured the relationship this way in his 2005 article, “Breathing life into hardware and software codesign”: “Hardware and software are like ice and water: each has its own distinct characteristics yet their essence is the same.” The analogy is useful because the two domains need different implementation techniques, even when they serve the same system behavior.
Why codesign needed a better bridge to implementation
Interest in codesign grew in the 1990s alongside hardware-synthesis tools and efforts to synthesize software. Early approaches aimed to derive hardware, software, and interfaces from one system specification. But increasingly complex processors, digital signal processors (DSPs), caches, and memory hierarchies made it difficult to optimize an abstract model accurately at low levels.
Free tools Windows power users keep installed
One-click scans. No signup required.
#1 Best Overall
- Designed for students and beginners looking to understand Digital Logic, fundamentals of FPGAs
- Features the Xilinx Artix 7 FPGA compatible with Vivado Design Suite WebPACK Edition (free download available from Xilinx)
- On board user interfaces include 16 user switches, 16 LEDs, 5 user pushbuttons, and a
- Expansion opportunities with four Pmod ports including 3 standard 12-pin Pmod ports and 1 dual
- Does NOT ship with micro USB cable
High-level function and architecture methods helped designers compare ideas, but their results did not always map cleanly to a realistic implementation. Conversely, detailed low-level models took effort to build and arrived too late to evaluate many architectural alternatives. A typical process—model and partition the system, hand the result to implementation teams, then revise it—could create repeated iterations and communication gaps.
Tabbara’s proposed remedy is a continuum of models: refine the system gradually, while letting implementation detail inform architectural decisions earlier. Rather than expecting a single model to be both maximally fast and maximally accurate, teams can select an abstraction appropriate to the question they need to answer.
How transaction-level modeling works
TLM describes behavior and communication in terms of transactions. A transaction represents an ordered relationship among events, with labels and a span of time. Transactions can be grouped into streams and can describe operations such as bus reads, writes, idle periods, or bursts. They can also be composed or decomposed, with predecessor/successor and parent/child relationships expressing how events fit together.
Rank #2
- Arty A7 comes in two FPGA variants: Arty A7-35T features Xilinx XC7A35TICSG324-1L. Arty A7-100T features the larger Xilinx XC7A100TCSG324-1.
- Internal clock speeds exceeding 450MHz, On-chip analog-to-digital converter (XADC), Programmable over JTAG and Quad-SPI Flash
- 256MB DDR3L with a 16-bit bus @ 667MHz, 16MB Quad-SPI Flash, USB-JTAG Programming circuitry, Powered from USB or any 7V-15V source
- 10/100 Mbps Ethernet, USB-UART Bridge
- 4 Switches, 4 Buttons, 1 Reset Button, 4 LEDs, 4 RGB LEDs, 4 Pmod connectors, shield connector
This makes communication visible as part of the model, rather than leaving it implicit in a block’s internal implementation. A designer can examine how components exchange data and how that behavior changes as the model becomes more detailed. In Tabbara’s account, TLM is therefore not simply a language feature: it is a cross-domain modeling concept that helps teams share behavioral and communication information.
Choose a model level for the question
The TLM workflow moves from fast functional exploration toward greater timing and implementation fidelity. The levels below describe the modeling continuum presented by Tabbara; they are not guarantees of a particular simulation speed or accuracy in every tool.
| Model level | What it emphasizes | Typical use | Trade-off |
|---|---|---|---|
| Programmers-view (PV) | Fast functional behavior with limited implementation detail | Explore system functions and compare architectural possibilities early | Runs at a higher abstraction, so it does not provide the timing and implementation detail of lower-level models |
| Programmers-view with timing (PVT) | Functional behavior plus timing; commonly combines a bus-functional hardware model with an instruction-set simulator abstraction | Evaluate timing-sensitive behavior and interactions between software execution and hardware communication | Adds timing context, but remains an abstraction rather than a cycle-accurate implementation model |
| Cycle-accurate or cycle-callable | Greater fidelity through a combination of bus-functional and register-transfer-level (RTL) abstractions | Investigate behavior where cycle-level detail or closer correspondence to implementation matters | Provides more detail than PV or PVT, but gives up some of the speed and simplicity of early abstraction |
The point is not to push every block to the most detailed level from the start. A team can use a faster model to decide which alternatives merit further work, then increase fidelity for the components or interactions that drive the decision.
Rank #3
- The best way to get started with FPGAs: Using a simple board with projects that build on eachother, now anyone can get started with FPGA development!
- Fun peripherals available: With 4 LEDs, 4 push-buttons, 7-segment display, USB connector, a VGA connector, and a PMOD (for expansion) you can have dozens of fun projects available to you out of the box!
- Works with Verilog and VHDL: No matter which programming language you want to get started with, the Go Board will work for you!
- No extra device required: Simply plug the Go Board into a USB port and go! Getting started with FPGAs has never been easier.
- Works with all operating systems: Windows, Mac, Linux
How to partition an embedded system between hardware and software
Partitioning is a system-level choice: decide which tasks should execute in software and which should be implemented in hardware, then evaluate the consequences together. TLM supports this exploration by allowing alternative functional blocks and their communication to be represented at different levels of detail.
- Model the system behavior and exchanges. Identify the functions and the reads, writes, bursts, idle periods, or other transactions through which components communicate. Making these exchanges explicit gives the architecture a common basis for comparison.
- Explore candidate placements at a functional level. Consider whether a task belongs in software or hardware without immediately committing to a detailed implementation. PV models are suited to this early exploration because they emphasize fast functional behavior.
- Add timing where it can change the decision. Use a PVT model when the interaction between software execution and hardware timing needs closer examination. A bus-functional model paired with an instruction-set simulator abstraction is one approach described in the article.
- Refine critical areas toward cycle-level detail. Use bus-functional and RTL abstractions for the components or paths where cycle behavior and implementation correspondence are important. Keep less critical parts at an appropriate higher level.
- Compare system constraints, not isolated blocks. Evaluate performance, size, and power consumption across the candidate designs. A change that improves one metric may affect another, so the useful result is the system-level trade-off rather than a local win considered alone.
This is an iterative process, not a formula that identifies a universally correct hardware/software boundary. TLM helps make alternatives comparable; it does not remove the need to choose constraints, interpret results, or validate the model against the intended architecture.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
How TLM supports verification and model substitution
A model can be replaced by a more detailed counterpart as design work progresses: functional, timed, bus-functional, RTL, and implementation models can be used at different speed-and-fidelity points. Comparing these models supports hardware/software co-verification, because software and hardware behavior can be assessed in the context of their interactions rather than as isolated deliverables.
Rank #4
- Digilent Basys 3 Artix-7 FPGA Trainer Board: Recommended for Introductory Users
The same approach can help investigate memory accesses, cache behavior, and bus utilization, and can inform decisions about moving a task between hardware and software. These are analysis uses, not automatic guarantees: conclusions depend on whether the chosen models represent the behavior and architecture relevant to the question.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Where SystemC and SystemVerilog fit
Tabbara names SystemC and SystemVerilog as system-level languages, but does not present either as a universal answer for every codesign problem. Embedded systems are heterogeneous, and application domains have different modeling needs. The central idea is to share behavior and communication information through TLM while allowing each domain to retain constructs suited to its work.
That distinction matters: choosing a language and choosing an abstraction strategy are related decisions, but they are not the same one. TLM is the bridge across modeling domains; a system-level language is one possible way to express models within that bridge.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallCrashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteBest Value
- [High-performance DSP] Sipeed Tang Primer 20K Core Module board is sodimm package,uses GW2A-LV18PG256C8I7 as the main chip, and hasmultiple internal resources, such as high-performance DSP,high-speed LvDs interface and BSRAM resources, on-boardDDR3 and PMIC. Users could use this CM board for rapiddevelopment and verify, and it's suitable for high-speedand low-cost situations.
- [Run RISC-V Code] Sipeed Tang Primer 20K gowin fpga development boards can burn the hardware code bitstream file ofPicoRV/Litex to Gw2A, and then use GW2A as acommon MCU. lt can run RISC-V code, conduct RISC-v soft core experiments
- [Verilog Design] Sipeed Tang Primer 20K Dock FPGA single board computer use verilog to design custom hardware func-tions on the basic of PicoRV/Litex lP core, and at thesame time use C language to write code running onPicoRV/Litex core.
- [Rich Peripheral interfaces] Sipeed Tang Primer 20K Dock is equipped with a wealth of pe-ripheral resources, such as onboard USB-JTAG & UARTperipheral , Ethernet PHY and RJ45 connector, USB2.0PHY，HDMIl output connector,Audio output circuit and3.5mm connector，RGB screen connector,DVP cameraconnector.
- [PMOD interfaces] Sipeed Tang Primer 20K Lite ext-board routes so many lOs todouble row pin headers and PMOD interfaces, with whichusers could easily connect other peripheral modules or cir-cuits for secondary development.
What codesign can—and cannot—automate
Tabbara describes automated synthesis as a productivity goal: given system constraints, tools could generate hardware, software, interfaces, and even an application-specific real-time operating system. The article does not establish that every tool flow can produce all of these automatically. The practical value of codesign and TLM is broader than one automation promise: they help engineers examine alternatives, communicate architectural intent, and refine models toward implementation.
As Tabbara puts it, “Codesign enables us to see beyond a particular hardware and software incarnation of an embedded systems design and analyze it at the core.” The emphasis is on reasoning about the system’s essential behavior and trade-offs before a particular implementation becomes the only one under consideration.
Source and historical context
This explanation follows Bassam Tabbara’s “Breathing life into hardware and software codesign,” published in 2005 and republished by Design-Reuse. Its discussion is a conceptual account of codesign and TLM, not a current tool comparison or a report of measured performance gains.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →
