SAM4L Datasheet, PDF (446/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
19.3 Block Diagram
Figure 19-1. Asynchronous Timer Block Diagram
CLK_AST
WAKE ENABLE
REGISTER
CLK_AST
CONTROL
REGISTER
CLK_AST
CSSEL
OSC32
EN PSEL
COUNTER
VALUE
RCSYS
APB clock
GCLK
CLK_AST_PRSC
32-bit
Prescaler
CLK_AST_CNT
32-bit
Counter
others
Periodic
Interrupts
Alarm
Interrupts
Wake
Control
Wake
OVF
Interrupt
Status
and
Control
IRQs
Events
DIGITAL
TUNER
REGISTER
PERIODIC
INTERVAL
REGISTER
ALARM
REGISTER
19.4 Product Dependencies
In order to use this module, other parts of the system must be configured correctly, as described
below.
19.4.1
Power Management
When the AST is enabled, it will remain clocked as long as its selected clock source is running. It
can also wake the CPU from the currently active sleep mode. Refer to Section 10. ”Power Man-
ager (PM)” on page 102 for details on the different sleep modes.
19.4.2 Clocks
The clock for the AST bus interface (CLK_AST) is generated by the Power Manager. This clock
is turned on by default, and can be enabled and disabled in the Power Manager.
A number of clocks can be selected as source for the internal prescaler clock CLK_AST_PRSC.
The prescaler, counter, and interrupt will function as long as this selected clock source is active.
The selected clock must be enabled in the System Control Interface (SCIF).
The following clock sources are available:
• System RC oscillator (RCSYS oscillator). This oscillator is always enabled, except in some
sleep modes. Refer to Section 42. ”Electrical Characteristics” on page 1106 for the
characteristic frequency of this oscillator.
• 32kHz clock (OSC32 or RC32). The oscillator must be enabled before use. Selection
between OSC32 and RC32 is done inside the Backup Power Manager module.
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