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6090D–DRMSD–12-Feb-07

ATSAM3308B

11. Reset and Power-down

During power up, the RESET input should be held low until the crystal oscillator and PLL are sta-

bilized, which takes max. 10 ms.

After the low to high transition of RESET, the following happens:

• All P24s enter an idle state.

• P16 program execution starts in built-in ROM.

The power-up sequence is as follows:

• STIN is sensed. If HIGH, then the built-in debugger is started.

• Addresses 0 & 1 from external ROM are checked. If "DR" is read, then control is transferred

to address 400H from external ROM.

•SMC is sensed. If LOW, then the built-in loader waits for SmartMedia presence detect

(SMPD). When detected, the firmware is down loaded from SmartMedia reserved sector 1

and started.

• An attempt is made to read the first two bytes of an external EEPROM or DataFlash. If "DR"

is read, then the built-in loader loads the firmware from the external EEPROM/DataFlash and

starts it.

• Firmware download from a host processor is assumed.

1.

The 0ACh byte is written to the host, this raises IRQ. The host can recognize that the

chip is ready to accept program download. Higher speed transfer can be reached by

polling the parallel interface status (CS = 0, A0 = 1, RD = 0).

2.

The host sends the firmware size (in words) on two bytes (Low byte first).

3.

The host sends the ATSAM3308B firmware. The firmware should begin with string

"DR".

4.

The 0ACh byte is written to the host, this raises IRQ. The host can recognize that the

chip has accepted the firmware.

5.

ATSAM3308B starts the firmware.

If PDWN is asserted low, then the crystal oscillator and PLL will be stopped. If the power switch

is used, then the chip enters a deep power down sleep mode, as power is removed from the

core. To exit power down, PDWN has to be asserted high, then RESET applied.

Other power reduction features allowing warm restart are controlled by firmware:

• P24s can be individually stopped.

• The clock frequency can be internally divided by 256.