Joshua Bowen, Product Marketing Engineer, 8-bit MCU business unit, Microchip Technology
It’s been over 50 years since the development of the first microcontroller. As these systems became more complex, many subsystems now require hundreds of thousands— if not millions—of MCUs. This puts a premium on delivering low-cost devices with high reliability and durability. With the advent of the Internet of Things (IoT) and the healthcare industry’s aggressive deployment of 8-bit MCUs, there has been even greater demand for them, as well as the need for these MCUs to provide additional capabilities for controlling portable, wireless and wearable devices.
The modern 8-bit MCU has risen to the challenge, maintaining their cost and reliability advantages while expanding user value through five key areas of innovation and advancement.
New Applications Drive New 8-bit MCU Requirements
Today’s IoT applications present the enormous challenge of implementing intelligence at scale. Entire cities are being upgraded with smart devices for applications ranging from smart streetlights to garage parking, which involves not just a single counter at the entrance, but individual detectors at every separate parking location.
In addition to their scale (and associated cost) challenges, IoT applications introduce many new MCU feature requirements. These include data gathering, processing and the communication of that data between networked devices.
Meeting these functional needs can often be accomplished using an 8-bit MCU with an on-chip analog-to-digital converter (ADC), and by having the core of the device remain in low-power mode. This is important for applications like the smart parking garages or connected street lighting examples we’ve referenced, where every mW of power usage is multiplied by what might be thousands of devices in systems that operate around the clock.
The latest 8-bit MCUs tackle these challenges with the same cost and reliability advantages they have always delivered. At the same time, they create new value for those developing applications that use portable battery-powered devices with strict power consumption limits. This new value is derived from five categories of advances in memory, power consumption, packaging, peripherals and design tools that, together, enable IoT system developers to accomplish the following with modern 8-bit MCUs:
1. Support more complex applications that require significantly more program code space
With the arrival of higher density Flash memory, 8-bit MCUs can now support significantly more complex applications. Using the increased memory, and techniques to leverage Core Independent Peripherals (CIPs), they are able to accommodate the requirements of new programs that demand additional code space/memory.
A key benefit of embedded Flash memory is its longevity. It can last years, which has been proven through rigorous automotive and functional safety testing. It also endures more write and erase cycles. 8-bit MCUs can feature from 384 bits to as much as 128 KB, or more, depending on what is required across a growing variety of applications.
2. Reduce power consumption for battery-powered applications
There are several ways that modern 8-bit MCUs support the new requirements of battery-powered applications.
One example is the nanoWatt XLP eXtreme Low Power PIC® MCU, which includes system supervisory circuits that are specially designed for these products. These circuits allow the MCUs to offer significantly lower currents for Run and Sleep (where extreme low-power applications spend the overwhelming majority—at least 90% or more of their time. This 8-bit MCU also features a Peripheral Module Disable capability and completely removes peripherals from the power rail and clock tree for zero power leakage. As a result, sleep currents remain below 20 nA, Brown-out Reset is reduced to 45 nA, Watch-dog Timer goes down to 220 nA, Real-time Clock/Calendar is kept to 470 nA and run currents go down to 50 μA/MHz. Even full analog and self-write capability is limited to 1.8V.
Maintaining these low currents across all of these functions increases portable-device battery life, which can be further improved through the availability of optimized Core Independent Peripherals (CIPs). Customizable CIPs add functionality while further reducing power usage.
3. Leveraging CIPs to create new system design opportunities
Today’s MCUs utilize a variety of CIPs to offer a number of benefits, especially for low power/low-cost designs. These CIPs feature built-in functionality that reduces power usage, and a modular design that simplifies how functions are implemented ranging from touch interfaces to sensor data accumulation and conditioning. Among the many benefits, CIPs can make it easier to implement complex software into hardware.
CIPs can execute a variety of tasks without any intervention from the microcontroller’s Central Processing Unit (CPU). Designers can program events using a pre-packaged approach based on peripherals, such as triggering General Purpose Input/Output (GPIO) or program interrupt events on multiple channels.
Figure 1 shows the wide variety of CIPs that are available for Microchip’s PIC® and AVR® MCUs. They address most of the functionality that developers expect in a cost-effective embedded controller.
CIPs improve reliability by reducing how much code overhead there is. Software conflicts are avoided when functions are implemented with hardware structures. Doing the same with peripheral interconnectivity increases system reliability by reducing external connections. Improved component reliability cuts the costs that are incurred over a project’s lifetime.
4. Meet the footprint, pin-count and memory needs of wireless/portable and wearable products
Another advantage of designing with an 8-pin device is that it is able to fit into the small packages to meet the needs of today’s space-sensitive wireless/portable and wearable products.
One packaging example is an 8-pin SOIC or 8-pin DFN. Another popular package is the 20-pin Very Thin Quad Flat Pack No-Leads (VQFN) with a 3 x 3 mm footprint. While adding more features can require more connections and larger packaging, it is possible to fit 8-bit MCUs into board spaces where 16-bit or 32-bit MCUs are too large.
If an 8-bit microcontroller’s increased capability requires larger area and more connections due to the increased system complexity it provides, larger packages, including 40-pin PDIP and VQFN and 44-pin TQFP versions, are used as well.
Many of the new 8-bit families provide extensive options both for pin count and memory. This is a big advantage when users want to complete their development on larger devices and then scale them down to smaller production devices after the code size has been optimized. This is especially important for packages used in cost-sensitive sensor and real-time control applications. Examples include Microchip’s PIC16F152XX microcontroller family whose feature set ranges from a 10-bit Analog-to-Digital Converter (ADC) and Peripheral Pin Select (PPS) to timers and digital communication peripherals. It also includes memory features, such as a Memory Access Partition (MAP) for data protection and bootloader applications.
5. Simplify and accelerate design-in
Newer 8-bit MCU development tools simplify processes that previously had to be hard-coded. Code configuration tools reduce application-development time while enabling more compact code without having to write it from scratch in assembly or iterate it multiple times.
For example, the PIC16F15244 Curiosity Nano Evaluation Kit delivers full programming and debugging capabilities and complete support for a new design (see Figure 2).
Click image to enlarge
Figure 2: PIC16F15244 Curiosity Nano Evaluation Kit (Part Number: EV09Z19A) is combined with two 100mil, 1x15 pin header strips in the Curiosity Nano Evaluation Kit to simplify design
8-bit MCUs are also supported by Integrated Development Environments (IDEs) that are free of charge and provide an environment for developing code for 8-bit (as well as 16- and 32-bit) MCUs. An example is Microchip’s MPLAB® X IDE. It enables simulation and interfacing with hardware tools and includes access plug-ins from both Microchip as well as third parties.
A New MCU Era
As microcontrollers have evolved, 8-bit MCUs have demonstrated particularly strong resilience and delivered a steady stream of application innovations from memory and power consumption advances to new options for packaging and peripherals. These devices offer larger memory for complex applications as well as new ways to simplify challenging applications, resulting in reduced development resources and lower costs for taking the MCU into production.
The latest generation of 8-bit MCUs has also broadened its usefulness. These MCUs are no longer used exclusively for data collection, but also to collect, process and transfer data across diverse IoT applications. They have also taken an important role in simplifying what have become increasingly complex IoT applications by offering much larger memory sizes and optimized peripherals.