Alternate Tick Timer

RTX Library version for Cortex™-M devices uses SysTick timer as RTX tick timer. The SysTick timer is Cortex-M core timer, thus common for all Cortex-M device variants. Some new dual core devices, such as LPC4300 devices, do not implement the SysTick timer in both cores. In this case, an alternate tick timer must be used for the core without SysTick timer.

The following functions provide an interface for an Alternate Tick Timer:

• os_tick_init()
  initializes hardware timer as system tick timer,
• os_tick_irqack()
  acknowledges hardware timer interrupt,
• OS_Tick_Handler()
  handles RTX tick interrupts and updates task scheduler.

Configuration

To configure an alternate peripheral timer as system tick timer, you have to:

1. implement the os_tick_init() and os_tick_irqack() functions in the RTX_Config.c configuration file.
2. replace the alternate timer interrupt vector with the OS_Tick_Handler in the Interrupt Vector Table in startup file.

Note

• An RTX_Blinky_RIT example, located in \Keil\ARM\Boards\MCB1700 directory, is a demo example, configured for alternate tick timer in Cortex-M3.