The ARM Cortex-M4 processor contains 37 registers in total. These registers can be categorized into general purpose registers, special purpose registers, and system control registers.
General Purpose Registers
The Cortex-M4 contains 13 general purpose registers named R0-R12. These registers are 32-bit wide and can be used for various computational and data manipulation purposes. The registers have the following functions:
- R0-R12 – General purpose usage
- R13 – Stack pointer
- R14 – Link register
- R15 – Program counter
So in total there are 16 general purpose registers in the Cortex-M4. They provide fast access locations for storage and retrieval of data during program execution.
Special Purpose Registers
The Cortex-M4 contains 7 special purpose 32-bit registers for specific functionality:
- APSR – Application Program Status Register
- IPSR – Interrupt Program Status Register
- EPSR – Execution Program Status Register
- IEPSR – Interrupt Exception Program Status Register
- PRIMASK – Priority Mask Register
- BASEPRI – Base Priority Mask Register
- FAULTMASK – Fault Mask Register
These special purpose registers are used by the processor to store status information during program execution, like the current execution state, pending interrupts, exceptions etc. They allow priority configuration for interrupts and faults.
System Control Registers
The Cortex-M4 contains 14 system control registers which manage and configure various aspects of the processor system. These include:
- VTOR – Vector Table Offset Register
- AIRCR – Application Interrupt and Reset Control Register
- SCR – System Control Register
- CCR – Configuration and Control Register
- SHPR1-SHPR3 – System Handler Priority Registers
- SHCSR – System Handler Control and State Register
- CFSR – Configurable Fault Status Register
- HFSR – HardFault Status Register
- DFSR – Debug Fault Status Register
- MMFAR – MemManage Fault Address Register
- BFAR – BusFault Address Register
- AFSR – Auxiliary Fault Status Register
These registers configure the exception/interrupt handling, memory protection, debug support and other system-level functions. They provide the processor system with control, status and configuration capabilities.
In total, the ARM Cortex-M4 processor contains:
- 16 general purpose registers
- 7 special purpose registers
- 14 system control registers
For a total of 37 registers that provide computational resources, status information, system configuration and exception handling capabilities that make Cortex-M4 a versatile, real-time capable microcontroller system.
The large number of registers in Cortex-M4 allow efficient data processing, interrupt handling, and flexible system configuration for embedded real-time applications. The general purpose registers provide fast temporary data storage locations for computations. The special purpose and system control registers give deep insight into the processor state and allow detailed configuration options.
In summary, the 37 registers in the ARM Cortex-M4 processor enable it to serve as a high-performance, real-time capable microcontroller system that can meet the needs of various complex embedded applications requiring efficiency, real-time responsiveness and robust configuration capabilities.