Customizable on-chip peripherals subvert traditional logic, TI helps engineers unleash their creativity

Customizable on-chip peripherals subvert traditional logic, TI helps engineers unleash their creativity

It’s a familiar scene in labs around the world: Design engineers push the limits, trying to add functionality or improve performance. However, when they drill down to the underlying system timing, they hit a design impasse. Because they may need to change the solution for a critical control signal. This situation limits engineers’ creativity and only hopes: “I wish I could customize the logic and timing within the control peripheral.” Now, with the Configurable Logic Blocks (CLBs) of C2000™ microcontrollers (MCUs), this wish has become a reality.

What is a CLB? CLB integrates an optimized high-speed programmable logic into a real-time controller such as a C2000 MCU, providing intelligent signal input/output (I/O) routing capabilities for key peripherals such as enhanced pulse width modulator (PWM), enhanced capture, enhanced quadrature encoder, and general purpose I/O, ultimately becoming an enhanced intellectual property (IP) block with system-level differentiation.

Figure 1: Example of a CLB tool unit block

As shown in Figure 1, the CLB tool consists of two, four, or eight logic blocks, each of which contains a complete set of optimized programmable logic cells, including:

• Three 4-input look-up tables (LUT4)

• Three 32-bit counters (Ctr32)

• Three 4-state finite state machines (FSM)

• Eight 3-input-output lookup tables (L3)

• A high level controller (HLC)

By configuring these blocks individually and connecting them together, you can generate custom logic schemes that provide novel solutions to complex system problems, such as writing application-specific logic for protection trigger conditions, enhancing types of soft-switching PWM, or implementing quadrature encoder position capture based on special conditions.

To facilitate development, TI created a graphical CLB configuration tool (shown in Figure 2) and integrated it directly into TI's Code Composer Studio™ integrated development environment for code development and debugging.

Figure 2: CLB tool configuration view

After configuration, the system will automatically generate the CLB tool output logic. The project compilation output is a *.h header file that describes the CLB tool configuration. During runtime initialization, the header file descriptor calls the C2000Ware DriverLib application programming interface function to configure the logic block.

Increasingly, design engineers are using CLB tools to explore new ways to differentiate their products. Matt Parnell, lead hardware engineer for Harman International's Lifestyle Audio division, has been using CLB to enhance his products.

According to Matt, they are always looking to “push the limits of design.”

“For example, we now move the main function’s software control loop to the CLB, offloading the user control logic and diagnostics. This reduces the per-cycle overhead of the 400kHz frequency, which is very effective and necessary. The bandwidth freed up by reducing the per-cycle overhead can be directly used to improve control functions,” said Matt.

He also talked about how the enhanced PWM (ePWM) peripheral integrates the signals “under the hood.”

“Within the CLB, designers can intercept the internal ePWM signals, including the action indicators and signals for deadband and logic conditions, and then create customized versions of the submodules. Harman has already used this capability to achieve new wins. The CLB adds a lot of customization to an already powerful device.”

The new CLB peripheral overcomes the barriers of control class design and provides a new toolset for creating differentiated solutions. The latest C2000Ware release includes 15 CLB examples; encoder examples are available in the MotorControl software development kit. Check out the training and application manuals to see how CLBs can disrupt traditional logic.