8.1.1 Access Types

Access control is based on the type of access. There are four main access types:

• Execute (Instruction Fetch)
• Data Read
• Write (Program/Erase)
• CRC

The Execute Access type indicates a CPU instruction fetch.

The Data Read Access type indicates either a CPU operand or a peripheral system bus data access.

The Write Access type indicates either a Flash programming or erase operation. In some instances, access control differentiates between program and erase operations.

The CRC Access type indicates an access by CRC hardware integrated into the NVM Controller. The integrated CRC function allows firmware integrity checking without exposing the region contents outside the NVM Controller. This capability can be used for integrity checking of execute-only memory. NVM CRC hardware is limited to calculating a 32-bit CRC over one or more consecutive four Kbyte Flash pages.