2 Floating-Point Unit (FPU)

Many control system designs typically start with simulation tools, where the algorithms are developed with floating-point math. These algorithms can then easily be ported to a microcontroller that has native floating-point math support. Floating-point math provides a large dynamic range, thereby making it easier to develop code compared to fixed-point math. The programmer no longer needs to worry about scaling and saturation. Additionally, robustness is improved since floating-point values do not wrap around the number line on an overflow or underflow, as they would in fixed-point math. These characteristics enable the high performance mathematical capabilities that are needed for advanced control systems. Also, the C2000 MCU architecture has been optimized to support high-level language programming, along with seamless support from a complete set of TI development tools.

The C2000 MCUs feature a C28x CPU that is designed around a 32-bit fixed-point accumulator-based architecture. It utilizes the best features of digital signal processors and microcontroller architectures. The addition of the FPU to the C28x fixed-point CPU enables the C2000 MCUs to support hardware IEEE-754 single-precision floating-point format operations. Devices with the C28x+FPU add an extended set of floating-point registers and instructions to the standard C28x architecture. These additional registers are: eight floating-point result registers, a floating-point status register, and a repeat block register. The repeat block adds zero overhead looping, which enables flexibility to the processor over the repeat single instruction. All of the registers are shadowed, except the repeat block register. Shadowing is useful with high priority interrupts for fast context save and restore of the floating-point registers.

Some C2000 MCUs are available with a FPU64 that provides hardware support for both IEEE-754 single-precision and double-precision floating-point operations. Devices with the C28x+FPU64 utilize the same registers as the FPU except for the addition of eight floating-point results extension registers for the double-precision floating-point operations. The FPU64 enhancements support all existing FPU single-precision floating-point instructions in addition to the 64-bit double-precision floating-point instructions.

The compiler tools provide C programming support for the CPU which makes it easy to write software, in addition to porting existing code. Since the FPU instructions are extensions of the standard C28x instruction set, most instructions operate in one or two pipeline cycles and some can be done in parallel. The FPU64 64-bit instructions operate in one to three pipeline cycles and some can be done in parallel, too. Floating-point performance dramatically enhances the mathematical computation horsepower used in signal processing and control algorithms.