Datasheet

SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
194
10.22.2 SysTick Reload Value Register
The LOAD register specifies the start value to load into the VAL register. See the register summary in Table 10-33
on page 192 for its attributes. The bit assignments are:
•RELOAD
Value to load into the VAL register when the counter is enabled and when it reaches 0, see “Calculating the RELOAD
value” .
10.22.2.1 Calculating the RELOAD value
The RELOAD value can be any value in the range 0x00000001-0x00FFFFFF. A start value of 0 is possible, but
has no effect because the SysTick exception request and COUNTFLAG are activated when counting from 1 to 0.
The RELOAD value is calculated according to its use:
 To generate a multi-shot timer with a period of N processor clock cycles, use a RELOAD value of N-1. For
example, if the SysTick interrupt is required every 100 clock pulses, set RELOAD to 99.
 To deliver a single SysTick interrupt after a delay of N processor clock cycles, use a RELOAD of value N. For
example, if a SysTick interrupt is required after 400 clock pulses, set RELOAD to 400.
31 302928 27 26 25 24
Reserved
23 22 21 20 19 18 17 16
RELOAD
15 14 13 12 11 10 9 8
RELOAD
76543 210
-RELOAD