Timer Tick Interrupt

The RTX kernel for ARM7™ and ARM9™ uses one of the standard ARM timers to generate a periodic interrupt. RTX kernel for Cortex™-M uses common SysTick timer. This interrupt is called the RTX kernel timer tick. For some of the RTX library functions, you must specify timeouts and delay intervals in number of RTX kernel timer ticks.

The parameters for the RTX kernel timer are selected in the RTX_Config.c configuration file. Each ARM microcontroller family provides a different peripherals that are supported with different RTX_Config.c files.

For example, the RTX_Config.c file for NXP LPC2100/LPC2200 allows to use Timer 0 or Timer 1 for the RTX kernel timer.

The timer clock value specifies the input clock frequency and depends on CPU clock and APB clock. For a device with CPU clock 60 MHz and VPB divider 4 the peripheral clock is 15MHz and therefore the value is set to 15000000.

The time tick value specifies the interval of the periodic RTX interrupt. The value 10000 us configures timer tick period of 0.01 seconds.