Datasheet

193
11011B–ATARM–21-Feb-12
SAM3N
10.22.2 SysTick Reload Value Register
The LOAD register specifies the start value to load into the VAL register. See the register sum-
mary in Table 10-33 on page 191 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 acti-
vated 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 30 29 28 27 26 25 24
Reserved
23 22 21 20 19 18 17 16
RELOAD
15 14 13 12 11 10 9 8
RELOAD
76543210
-RELOAD