FEATURE MCUS & MPUS NEW GENERATION OF 8-BIT MCUS
Jin Xu, Asia Pacific Business Development Manager, MCU8 Division at Microchip Technology Inc. explores the growth potentials for new 8-bit MCU Peripherals and the future capabilities
T
here is a new generation of 8-bit microcontrollers that bring a new level
of design flexibility through the integration of “Core Independent Peripherals”. These configurable peripherals, such as a simple digital timer or a complex AC/DC power supply combined with integrated intelligent analogue, offer balanced and bespoke solutions to many design challenges. Where traditional 8-bit MCUs have fallen short, these new 8-bit microcontrollers can step in to the breach. Microcontrollers have seen many advances since the introduction of the first Read Only Memory (ROM) MCU over 40 years ago. 8-bit microcontrollers, in particular, have gone from a simple logic controller to a fully integrated smart IC with analogue features. The classic view of an 8-bit microcontroller’s peripherals was one where each module was designed to perform a fixed function, and nothing more. The latest 8-bit generation was created to be different, from the ground up, which is a paradigm shift that requires a whole new end-product design approach. These new 8-bit microcontrollers have
integrated a number of unique peripherals that can perform multiple functions and tasks, as needed. In addition, these peripherals can be configured and combined to create new functions that were previously difficult to execute and in some cases impossible with other types of microcontrollers. Most of these new peripherals can operate independently, without any core supervision, thus reducing reliance on the CPU to perform the necessary tasks. Furthermore, many of these peripherals can be used in SLEEP mode for the most power-sensitive applications.
USING CORE-INDEPENDENT PERIPHERALS One of the most commonly used peripherals from this new crop is the Configurable Logic Cell (CLC). This is a very simple yet powerful module that offers standard logic functions—such as AND, OR, XOR, SR Latch, and J-K Flip Flop—which the user can configure to create logic gates for signal conditioning. The input and output signals of the CLC
module can be connected to any of the I/Os, peripherals or registers, via internal connections. It can be used as a simple signal router, glue logic, or an intelligent state machine for wake-up control. The
18 MAY 2016 | ELECTRONICS Figure 1:
An Example Numerically Controlled Oscillator Application
used on its own, the magic really happens when multiple modules are combined together to create different functions. Other peripherals, such as the Angular Timer (AT), the Signal Measurement Timer (SMT) and the Math Accelerator (MathAcc), are a bit more sophisticated when compared to the CLC or NCO modules. The AT can be used to measure any periodic signals—such as optical encoders, zero-cross detectors and Hall sensors—for motor-control and AC- power applications, regardless of the motor’s speed or the signal’s frequency. The AT module performs instantaneous
time/angle domain transformation, all in hardware, and once again without any additional CPU overhead. Handling this task with a traditional microcontroller would typically require multiple timers to count and measure units of time, and then transform the values into the phase-angle domain through mathematical calculations (via firmware); or lookup tables stored in program memory, if the period is known. The traditional approach requires more
traditional microcontroller requires an external Programmable Logic Device (PLD) or additional coding to get the desired logic controls, and even that setup doesn’t provide all of the CLC’s flexibility. The Numerically Controlled Oscillator
(NCO) is another configurable module that can be used as a 20-bit timer or a PWM controller with high-resolution, variable- frequency control, as shown in Figure 1. This is not a traditional PWM/timer, where the performance and features are almost exactly the opposite of each other.
CONTROLLED OSCILLATOR APPLICATION The NCO, with its higher resolution and linear frequency control, can help to simplify a complex control algorithm commonly used in many power supply applications, such as lighting ballast control with dimming functionality, by controlling the circuit current very accurately. Another use of the NCO is to drive the audio alert of a smoke alarm, as it provides the variable frequency control to easily change the pitch of an alarm tone. The finer control of the generated frequency also allows better tuning of the tone and pitch of the sound generated, without the need for any external analogue components. While this integrated peripheral can be
firmware setup and CPU resources for the math, as well as the size constraint of the lookup table that could limit the number of values available, and thus lead to approximation and inaccuracy. The AT module can automatically generate interrupts and events, directly, based on the phase-angle value configured by the designer. Additionally, the AT has three Compare/Capture PWM (CCP) functions at the user’s disposal. To sum up, Core-Independent
Peripherals provide more flexibility for designers, by giving them the ability to configure and combine several peripherals, creating multiple application functions without sacrificing CPU performance or power consumption. These new hardware peripherals remove the traditional dependency on the core, and add determinism to the overall system design. The newest generation of 8-bit
microcontrollers are then considered more capable and powerful than the traditional 8-bit MCU, and can often achieve higher performance than the software-centric approach of 32-bit MCUs, by executing many functions with integrated core- independent hardware.
Microchip Technology Inc.
www.microchip.com T: 0118 921 5800
/ ELECTRONICS
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