SAMD21 System Control Block (SCB) Overview

Last modified by Microchip on 2023/11/09 09:01

The System Control Block (SCB) is the programmer's model interface to the processor. It provides system implementation information and system control, including configuration, control, and reporting of system exceptions. The SCB registers are:

AddressNameTypeReset valueDescription
0xE000ED00CPUIDRO0x410CC601aCPUID Register
0xE000ED04ICSRRWb0x00000000Interrupt Control and State Register
0xE000ED08VTORcRW0x00000000Vector Table Offset Register
0xE000ED0CAIRCRRWb0xFA050000Application Interrupt and Reset Control Register
0xE000ED10SCRRW0x00000000System Control Register
0xE000ED14CCRRO0x00000204Configuration and Control Register
0xE000ED1CSHPR2RW0x00000000System Handler Priority Register 2
0xE000ED20SHPR3RW0x00000000System Handler Priority Register 3

CPUID Register

The CPUID register contains the processor part number, version, and implementation information.

Interrupt Control and State Register

  • The ICSR provides:
    • A set-pending bit for the Non-Maskable Interrupt (NMI) exception.
    • Set-pending and clear-pending bits for the PendSV and SysTick exceptions
  • The ICSR indicates:
    • The exception number of the highest priority pending exception.

Vector Table Offset Register

If implemented, the VTOR indicates the offset of the vector table base address from memory address 0x00000000.

Application Interrupt and Reset Control Register

The AIRCR provides endian status for data accesses and resets control of the system.

System Control Register

The SCR controls features of entry to and exit from low power state.

Configuration and Control Register

The CCR is a read-only register and indicates some aspects of the behavior of the Arm® Cortex®-M0+ processor.

System Handler Priority Registers

The SHPR2-SHPR3 registers set the priority level (0 to 192) of the system exception handlers that have configurable priority.
SHPR2-SHPR3 are word accessible.

Ensure software uses aligned 32-bit word size transactions to access all the SCB registers.