SAM7S256_14 Datasheet, PDF (144/775 Pages) ATMEL Corporation – ARM-based Flash MCU

21.3 Device Initialization with USB
Initialization follows the steps described below:
1. FIQ initialization
1. Stack setup for ARM supervisor mode
2. Setup the Embedded Flash Controller
3. External Clock detection
4. Main oscillator frequency detection if no external clock detected
5. Switch Master Clock on Main Oscillator
6. Copy code into SRAM
7. C variable initialization
8. PLL setup: PLL is initialized to generate a 48 MHz clock necessary to use the USB Device
9. Disable of the Watchdog and enable of the user reset
10. Initialization of the USB Device Port
11. Jump to SAM-BA Boot sequence (see “SAM-BA Boot” on page 145)
21.4 Device Initialization without USB
Initialization follows the steps described below:
1. FIQ initialization
1. Stack setup for ARM supervisor mode
2. Setup the Embedded Flash Controller
3. External Clock detection
4. Main oscillator frequency detection if no external clock detected
5. Switch Master Clock on Main Oscillator
6. Copy code into SRAM
7. C variable initialization
8. PLL setup: PLL is initialized to generate a 48 MHz clock
9. Disable of the Watchdog and enable of the user reset
10. Jump to SAM-BA Boot sequence (see “SAM-BA Boot” below)
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
144