CPU
The ARM® Cortex®-M4 processor with floating-point unit (FPU) has a 32-bit instruction set (Thumb®-2 technology) that implements a superset of 16 and 32-bit instructions to maximize code density and performance.
This processor implements several features that enable energy-efficient arithmetic and high-performance signal processing including:
- Digital signal processing (DSP) instructions
- Single-cycle multiply and accumulate (MAC) instructions
- Hardware divide
- 8 and 16-bit single instruction multiple data (SIMD) instructions
- Single-precision floating-point unit (FPU)
The ARM Cortex Microcontroller Software Interface Standard (CMSIS) hardware abstraction layer for the ARM Cortex processor series is implemented and available for the M4 CPU.
Real-time execution is highly deterministic in thread mode, to and from sleep modes, and when handling events at configurable priority levels via the Nested Vectored Interrupt Controller (NVIC).
Executing code from flash will have a wait state penalty on the nRF52 Series. An instruction cache can be enabled to minimize flash wait states when fetching instructions. For more information on cache, see Cache. The section Electrical specification shows CPU performance parameters including wait states in different modes, CPU current and efficiency, and processing power and efficiency based on the CoreMark® benchmark.
Floating point interrupt
The floating point unit (FPU) may generate exceptions when used due to e.g. overflow or underflow. These exceptions will trigger the FPU interrupt (see Instantiation). To clear the IRQ line when an exception has occurred, the relevant exception bit within the FPSCR register needs to be cleared. For more information about the FPSCR or other FPU registers, see Cortex-M4 Devices Generic User Guide.
Electrical specification
CPU performance
The CPU clock speed is 64 MHz. Current and efficiency data is taken when in System ON and the CPU is executing the CoreMark™ benchmark. It includes power regulator and clock base currents. All other blocks are IDLE.
| Symbol | Description | Min. | Typ. | Max. | Units | ||||
|---|---|---|---|---|---|---|---|---|---|
| WFLASH | CPU wait states, running from flash, cache disabled | 0 | 2 | ||||||
| WFLASHCACHE | CPU wait states, running from flash, cache enabled | 0 | 3 | ||||||
| WRAM | CPU wait states, running from RAM | 0 | |||||||
| IDDFLASHCACHE | CPU current, running from flash, cache enabled, LDO | 7.4 | mA | ||||||
| IDDFLASHCACHEDCDC | CPU current, running from flash, cache enabled, DCDC 3V | 3.7 | mA | ||||||
| IDDFLASH | CPU current, running from flash, cache disabled, LDO | 8.0 | mA | ||||||
| IDDFLASHDCDC | CPU current, running from flash, cache disabled, DCDC 3V | 3.9 | mA | ||||||
| IDDRAM | CPU current, running from RAM, LDO | 6.7 | mA | ||||||
| IDDRAMDCDC | CPU current, running from RAM, DCDC 3V | 3.3 | mA | ||||||
| IDDFLASH/MHz | CPU efficiency, running from flash, cache enabled, LDO | 125 | µA/MHz | ||||||
| IDDFLASHDCDC/MHz | CPU efficiency, running from flash, cache enabled, DCDC 3V | 58 | µA/MHz | ||||||
| CMFLASH | CoreMark1, running from flash, cache enabled | 215 | CoreMark | ||||||
| CMFLASH/MHz | CoreMark per MHz, running from flash, cache enabled | 3.36 | CoreMark/MHz | ||||||
| CMFLASH/mA | CoreMark per mA, running from flash, cache enabled, DCDC 3V | 58 | CoreMark/mA |
CPU and support module configuration
The ARM® Cortex®-M4 processor has a number of CPU options and support modules implemented on the device.
| Option / Module | Description | Implemented |
|---|---|---|
| Core options | ||
| NVIC | Nested Vector Interrupt Controller | 37 vectors |
| PRIORITIES | Priority bits | 3 |
| WIC | Wakeup Interrupt Controller | NO |
| Endianness | Memory system endianness | Little endian |
| Bit Banding | Bit banded memory | NO |
| DWT | Data Watchpoint and Trace | YES |
| SysTick | System tick timer | YES |
| Modules | ||
| MPU | Memory protection unit | YES |
| FPU | Floating point unit | YES |
| DAP | Debug Access Port | YES |
| ETM | Embedded Trace Macrocell | YES |
| ITM | Instrumentation Trace Macrocell | YES |
| TPIU | Trace Port Interface Unit | YES |
| ETB | Embedded Trace Buffer | NO |
| FPB | Flash Patch and Breakpoint Unit | YES |
| HTM | AHB Trace Macrocell | NO |