Const and volatile type qualifiers

const

const means that something is not modifiable, so a data object that is declared with const as a part of its type specification must not be assigned to in any way during the run of a program.

volatile

The use of volatile ensures that the compiler always carries out the memory accesses, rather than optimizing them out (for example if the access is in a loop).

Memorymapped access to a register

Example 1

In the example below the register 32 bit register located at address 0x40000 can be accessed

Links

• Const and volatile
• armcc/tcc: Placing C variables at specific addresses - memory-mapped peripherals
• Use of 'const' and 'volatile'