The best design for upgrading from 8-bit MCU to 32-bit MCU

An age-old embedded design question is, should you use an 8-bit or 32-bit core in your new design? If you ask your colleagues, you may find that their opinions differ widely. Like it or not, 32-bit cores are here to stay. So what does this mean? It means that one day, no matter how hard you try to avoid it, you will have to move from your favorite 8-bit core to a new, complex 32-bit core. Is this kind of migration painful? With the right techniques and methods, it is not. The

current MCU market is divided into three segments, 8-bit, 16-bit, and 32-bit cores (4-bit core MCUs are now quite rare, so they are ignored in this comparison). For each of these three segments, the size is roughly the same. Traditionally, 8-bit cores have the largest market share. According to some analyst reports, 32-bit cores may have surpassed 8-bit cores in market share. Even if they have not yet surpassed, it will not be long. The 32-bit core market share is by far the fastest growing. 8-bit and 16-bit cores are still growing, but not nearly as fast as 32-bit cores (8-bit cores are still growing faster than 16-bit cores).

For a long time, many people believed that 16-bit MCUs might be replaced by 8-bit and 32-bit MCUs. Today's 32-bit MCU devices are manufactured using the latest technology (compared to 8-bit and 16-bit cores).

MCU manufacturers are able to use these latest technologies, making 32-bit MCUs smaller and therefore cheaper. Due to the price and performance of 32-bit MCUs, many analysts believe that design engineers will jump out of the 16-bit world and go directly to high-performance products to future-proof their designs.

8-bit MCUs have reached their limits in terms of performance and memory handling capabilities. This is why 16-bit and 32-bit MCUs exist today. As the industry develops along the trajectory of Moore's Law, 32-bit MCUs are becoming smaller and cheaper, and they are also competitive in the traditional 8-bit and 16-bit world.

These new 32-bit MCUs have higher processing power than 8-bit and 16-bit MCUs. Typical 8-bit MCUs have speeds between 10 and 30 MIPS. 16-bit MCUs are between 20 and 40 MIPS. New 32-bit MCUs typically have 80 to 100 MIPS of processing power! This is a major improvement in processing power and speed.

Many 32-bit MCUs are smaller and typically have lower power consumption than 8-bit and 16-bit MCUs. Smaller size generally means better power consumption, lower current consumption, and lower effective input voltage. Some new products have almost unmeasurable sleep currents and offer input voltages as low as 0.5V. This gives 32-bit MCUs a huge advantage. In today's market, power is king. Even if an application is not battery powered, today's designers still have to consider power consumption. For applications that plug into the grid, they still have to be "green" for a variety of reasons. Some top products must be targeted for marketing purposes or because of government mandates and standards. For example, the latest consumer electronic devices are now Energy Star compliant. If

you are currently using an 8-bit MCU, you may want to consider a 32-bit MCU for your next design. Even if the next generation of designs continues to use 8-bit MCUs, there are many steps and methods to help you prepare for the eventual migration. Doing some research today and making the right decisions can ensure the design of tomorrow.

When you start to think about moving to 32-bit MCUs, you may think that there will be some problems. For example, you think you need to learn a new architecture; you may need to rewrite all your code to work with the new core; perhaps you feel that 32-bit MCUs are too difficult and complicated. They are not designed for ease of use, but for performance, which means that you will have to consider the thousands of registers they have; perhaps you are concerned about the possibility of having to learn a whole new set of software tools, and you will need to familiarize yourself with new hardware tools; or perhaps you think that 32-bit MCUs are not targeted at your application and you can't find the right set of peripherals for your design. You may be concerned about one or more of these issues, but are they all necessary considerations? Let's analyze them separately.

Most designers think that when they move from 8-bit MCUs to 32-bit MCUs, they will have to learn a new architecture. The problem is that most companies have their own old 8-bit MCU product line and their new 32-bit MCU product line. They may still release a few new products each year for the 8-bit product line, and they want to take the opportunity to learn from their mistakes and correct them in the 32-bit line. You may not find the same peripheral parts on the device. The code between the different families is not compatible, or there is no pin compatibility, so you will have to redo the entire board.

Although it is true that you cannot migrate without changing the core of the design, you also hope that you don’t have to learn everything again. Some companies are starting to release new products with the exact same set of peripheral components between the 8-bit version and the 32-bit version. The only thing that changes in the component is its core. Everything else, including the pin layout location, remains the same. If you are using an 8-bit MCU today, you can migrate to the company’s 32-bit MCU tomorrow and still use the same printed circuit board. An example of this is the recent release of the PSoC® 3 and PSoC 5 architectures by Cypress Semiconductor. The two architectures have the same peripheral components, packages, and pins. The PSoC 3 architecture, with its new single-cycle/instruction 8051, runs at frequencies up to 67 MHz and is easily compatible with the PSoC 5 version. The PSoC 5 version uses an ARM® Cortex™-M3 processor running at up to 80 MHz. This type of product makes migration from one architecture to the other easy.

 
Figure 1: Click a button and go from 8-bit to 32-bit

People also think that you will have to rewrite all your code for the new 32-bit product. That is not always the case. For many of these new products that have matching peripherals between the 8-bit and 32-bit cores, their firmware is also compatible. These chips use a high-level language such as C, and you can write one set of code and choose to compile for the 8-bit product, or choose the 32-bit product and recompile. You can take a slightly more complicated approach and write code in a high-level language and still call registers for a specific core, and if you follow the spirit of high-level programming, porting is still fairly easy. [page]

You might think about what about tools? You may be more concerned with the integrated development environment (IDE) than the specific core you are using. Once you have mastered it, you don't want to learn a new one. But what if you had an IDE that worked on both architectures? An example of this is the new PSoC Creator™ software from Cypress. It is an integrated development environment (IDE) that works with both 8-bit devices and 32-bit devices. A good way to future-proof your design is to choose products today (even if you are still working with 8-bit cores) that allow you to use the same tools for both 8-bit and 32-bit designs.

Similar to software tools, hardware tools are also emerging in terms of cross-platform applications. Some companies have developed modular systems with hardware development tool boxes. This allows you to pull out the 8-bit module and replace it with a 32-bit module. Everything else on the board remains the same. They usually use the same programming and debugging tools. You can really learn once and apply everywhere.

The real consideration is that many companies have developed 32-bit products for different markets where they sell 8-bit products. This means that you can't find the right 32-bit product to support your design. Therefore, you not only pay more for the 32-bit product, but also spend more on external discrete devices. But what if you could design your own chip? Similar to FPGAs or CPLDs, but in a simpler way using a graphical environment? Wouldn't it be great if you could implement your own design in a tool, create it, and program it into the device? Too good to be true, right? Of course not. With PSoC 3 and PSoC 5, this is possible. You can now design peripheral devices around the 32-bit core and make sure they are the right devices for your design. With these new tools, you can design the way you want.

 
Figure 2: Design schematic in PSoC Creator software

Now more than ever, flexibility is more important to designers. The market is changing faster than ever before, competition is increasing every day, and everyone is striving for lower costs. Choosing the right 8-bit device family today can protect you tomorrow. Using these new tools, you can design with an 8-bit MCU, perhaps as a base version of your company's product portfolio, and then you can take your task, use the same project files, and migrate it to a 32-bit core. Now you can add more performance. Soon, it will become your company's high-end specialty product, earning higher profits.

32-bit MCUs are the next generation of embedded design. When to take the step is up to you. It may be now, it may be in a few years, but at some point, your 8-bit MCU will have exhausted its capabilities and will not be able to meet the ever-changing needs of today's market. Most designers dread this step. But it doesn't have to be painful. We've looked at some actions you can take today to make the transition as smooth as possible. If you are still designing with an 8-bit core today, make sure the product family you are using has a 32-bit counterpart. The same is true for tools. Many companies now offer the same software and hardware tools that can be used on different architectures. Choosing the right device (8-bit or 32-bit) today will help you and your design be more successful tomorrow.