at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 73

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

13.3
6384B–ATARM–15-Dec-08
Device Initialization
Initialization follows the steps described below:
Table 13-1.
Note:
Table 13-2.
Note:
Table 13-3.
Note:
Boot in DBGU
Boot on USB
Boot in DBGU
Boot on USB
3.0
4.433619
6.0
1. Stack setup for ARM supervisor mode
2. Main Oscillator Frequency Detection
3. C variable initialization
4. PLL setup: PLLB is initialized to generate a 48 MHz clock necessary to use the USB
7.3728
11.05920
14.7456
Device. A register located in the Power Management Controller (PMC) determines the
frequency of the main oscillator and thus the correct factor for the PLLB.
– If internal RC Oscillator is used (OSCSEL = 0) and Main Oscillator is active,
– If internal RC Oscillator is used (OSCSEL = 0) and Main Oscillator is bypassed,
– If an external 32768 Hz Oscillator is used (OSCSEL = 1), defines the crystals
13-1
oscillator. als supported by the Boot Program.
Table 13-2
main oscillator. .
supported by the Boot Program.
Boot Program.
Any other crystal can be used but it prevents using the USB.
Any other crystal can be used but it prevents using the USB.
Booting either on USB or on DBGU is possible with any of these input frequencies.
defines the crystals supported by the Boot Program when using the internal RC
Crystals Supported by Software Auto-Detection (MHz)
Crystals Supported by Software Auto-Detection (MHz)
Crystals Supported by Software Auto-Detection (MHz)
defines the frequencies supported by the Boot Program when bypass-ing
3.0
Yes
Yes
3.0
Yes
Yes
3.2768
6.144
7.864320
12.0
16.0
4.608
8.0
Yes
Yes
8.0
Yes
Yes
3.6864
4.9152
6.4
8.0
12.288
17.734470
Table 13-3
AT91SAM9G20 Preliminary
20
Yes
Yes
defines the crystals supported by the
18.432
Yes
Yes
3.84
5.0
6.5536
9.8304
13.56
18.432
50
Yes
Yes
Other
Yes
No
4.0
5.24288
7.159090
10.0
14.31818
20.0
Other
Yes
No
TTable
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