Class _stka: SysTick timer (STK)

Relatives

• Interrupts
  • (systick,irq)
• Registers
  • (systick,tenms)
  • (systick,onems)

According to PM0056, the _stka class SysTick timer has a tenms logical register that holds the factory calibration value for a 10 ms period.

In fact, for the STM32F103, the value of tenms is 9000. Then, the calibration value minus 1 gives a 1 ms period (yes, ONE ms) when the SysTick is clocked at 9 MHz (72 MHz / 8).

For that reason, HWA also provides a onems logical register that is the same as tenms but maybe less confusing.

//  1 ms period when AHB is clocked at 9 MHz
//
hw( configure, systick,
    clock,     ahb,
    reload,    (hw(read, (systick,onems)) - 1) & 0xFFFFFF,
    run,       yes );

Interface

• Configuration

hw|hwa( configure,   systick,
 
      [ clock,       ahb                // Clock source
                   | ahb/8 ],
 
      [ reload,      x, ]               // Any value in 0..0xFFFFFF
 
      [ run,         yes | no ] );

• Run control

hw|hwa( turn, systick, on | off );

• Count value

uint32_t v = hw( read, systick );       // Returns the current value of the timer