T
stop_min
= 1 × divided clock source 1 × clock source period
T
stop_max
= 2 × divided clock source p 2 × clock source periods
The On-Demand function can be disabled individually for each clock source by clearing the ONDEMAND
bit located in each clock source controller. Consequently, the clock will always run whatever the clock
request status is. This has the effect of removing the clock source startup time at the cost of power
consumption.
The clock request mechanism can be configured to work in standby mode by setting the RUNSDTBY bits
of the modules, see
.
15.6. Power Consumption vs. Speed
When targeting for either a low-power or a fast acting system, some considerations have to be taken into
account due to the nature of the asynchronous clocking of the peripherals:
If clocking a peripheral with a very low clock, the active power consumption of the peripheral will be lower.
At the same time the synchronization to the synchronous (CPU) clock domain is dependent on the
peripheral clock speed, and will take longer with a slower peripheral clock. This will cause worse
response times and longer synchronization delays.
15.7. Clocks after Reset
On any Reset the synchronous clocks start to their initial state:
•
DFLL48M is enabled and configured to run at 48MHz
•
Generic Generator 0 uses DFLL48M as source and generates GCLK_MAIN
•
CPU and BUS clocks are undivided
On a Power Reset, the 32KHz clock sources are reset and the GCLK module starts to its initial state:
•
All Generic Clock Generators are disabled except
–
Generator 0 is using DFLL48M at 48MHz as source and generates GCLK_MAIN
•
All Peripheral Channels in GCLK are disabled.
On a User Reset the GCLK module starts to its initial state, except for:
•
Generic Clocks that are write-locked, i.e., the according WRTLOCK is set to 1 prior to Reset
Related Links
on page 181
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
120