SAM3X8E Atmel Corporation, SAM3X8E Datasheet - Page 325

• Manufacturer Part Number: SAM3X8E
• Manufacturer: Atmel Corporation

21. SAM3X/A Boot Program
21.1
21.2
Figure 21-1. Boot Program Algorithm Flow Diagram
21.3
11057A–ATARM–17-Feb-12
11057A–ATARM–17-Feb-12
Description
Flow Diagram
Device Initialization
The SAM-BA
into the different memories of the product.
The Boot Program implements the algorithm in
The SAM-BA Boot program seeks to detect a source clock either from the embedded main oscil-
lator with external crystal (main oscillator enabled) or from a 12 MHz signal applied to the XIN
pin (Main oscillator in bypass mode).
If a clock is found from the two possible sources above, the boot program checks to verify that
the frequency is 12 MHz (taking into account the frequency range of the 32 kHz RC oscillator). If
the frequency is 12 MHz, USB activation is allowed, else (no clock or frequency other than
12MHz), the internal 12 MHz RC oscillator is used as main clock and USB clock is not allowed
due to frequency drift of the 12 MHz RC oscillator.
Initialization follows the steps described below:
Device
Setup
1. Stack setup
2. Setup the Embedded Flash Controller
3. External Clock detection (quartz or external clock on XIN)
4. If quartz or external clock is 12.000 MHz, allow USB activation
5. Else, does not allow USB activation and use internal RC 12 MHz
6. Main oscillator frequency detection if no external clock detected
7. Switch Master Clock on Main Oscillator
8. C variable initialization
9. PLLA setup: PLLA is initialized to generate a 48 MHz clock
10. UPLL setup in case of USB activation allowed
11. Disable of the Watchdog
12. Initialization of the UART (115200 bauds, 8, N, 1)
13. Initialization of the USB Device Port (in case of USB activation allowed)
14. Wait for one of the following events
®
Boot Program integrates an array of programs permitting download and/or upload
Run SAM-BA Monitor
USB Enumeration
Successful ?
Yes
No
Figure
Run SAM-BA Monitor
Character # received
No
from UART?
21-1.
Yes
SAM3X/A
SAM3X/A
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