AT91SAM7S32-AI ATMEL [ATMEL Corporation], AT91SAM7S32-AI Datasheet - Page 151

• Manufacturer Part Number: AT91SAM7S32-AI
• Description: AT91 ARM Thumb-based Microcontrollers
• Manufacturer: ATMEL [ATMEL Corporation]

Clock Generator
Description
Slow Clock RC
Oscillator
Main Oscillator
Main Oscillator
Connections
6071A–ATARM–28-Oct-04
The Clock Generator is made up of 1 PLL, a Main Oscillator, an RC Oscillator and It provides
the following clocks:
•
•
•
The Clock Generator User Interface is embedded within the Power Management Controller
one and is described in “Power Management Controller (PMC) User Interface” on page 161.
However, the Clock Generator registers are named CKGR_.
The slow clock is the output of the RC Oscillator and is the only clock considered permanent in
a system that includes the Power Management Controller. It is mandatory in the operations of
the PMC.
The user has to take the possible drifts of the RC Oscillator into account. More details are
given in the DC Characteristics section of the product datasheet.
Figure 53 shows the Main Oscillator block diagram.
Figure 53. Main Oscillator Block Diagram
The Clock Generator integrates a Main Oscillator that is designed for a 3 to 20 MHz funda-
mental crystal. The typical crystal connection is illustrated in Figure 54. The 1 k
only required for crystals with frequencies lower than 8 MHz. The oscillator contains 25 pF
capacitors on each XIN and XOUT pin. Consequently, CL1 and CL2 can be removed when a
crystal with a load capacitance of 12.5 pF is used. For further details on the electrical charac-
teristics of the Main Oscillator, see the DC Characteristics section of the product datasheet.
SLCK, the Slow Clock, which is the only permanent clock within the system.
MAINCK is the output of the Main Oscillator
PLLCK is the output of the Divider and PLL block
Slow Clock
XOUT
SLCK
XIN
Main Clock
AT91SAM7S32 Preliminary
OSCOUNT
Frequency
Oscillator
Oscillator
MOSCEN
Counter
Counter
Main
Main
Main Clock
MAINCK
MAINRDY
MOSCS
MAINF
resistor is
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