SAM7S256_14 Datasheet, PDF (29/775 Pages) ATMEL Corporation – ARM-based Flash MCU

9.2 Clock Generator
The Clock Generator embeds one low-power RC Oscillator, one Main Oscillator and one PLL with the following
characteristics:
z RC Oscillator ranges between 22 kHz and 42 kHz
z Main Oscillator frequency ranges between 3 and 20 MHz
z Main Oscillator can be bypassed
z PLL output ranges between 80 and 220 MHz
It provides SLCK, MAINCK and PLLCK.
Figure 9-3. Clock Generator Block Diagram
Clock Generator
Embedded
RC
Oscillator
Slow Clock
SLCK
XIN
XOUT
Main
Oscillator
Main Clock
MAINCK
PLLRC
PLL and
Divider
PLL Clock
PLLCK
Status Control
Power
Management
Controller
9.3 Power Management Controller
The Power Management Controller uses the Clock Generator outputs to provide:
z the Processor Clock PCK
z the Master Clock MCK
z the USB Clock UDPCK (not present on SAM7S32/16)
z all the peripheral clocks, independently controllable
z three programmable clock outputs
The Master Clock (MCK) is programmable from a few hundred Hz to the maximum operating frequency of the device.
The Processor Clock (PCK) switches off when entering processor idle mode, thus allowing reduced power consumption
while waiting for an interrupt.
SAM7S Series [DATASHEET] 29
6175M–ATARM–26-Oct-12