AT91SAM9G46B-CU 查看數據表（PDF） - Atmel Corporation

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AT91SAM9G46B-CU

SMART ARM-based Embedded MPU

Atmel Corporation 

52.3.9 USB High Speed Host Port (UHPHS) and Device Port (UDPHS)

52.3.9.1 UHPHS/UDPHS: USB Does Not Start after Power-up

The USB may not start properly at first use after power-up.

Booting out of the internal ROM fixes this issue because the workaround below is applied in the ROM Code.

Problem Fix/Workaround

There are two possible workarounds:

1. Apply a hardware reset (NRST) after power-up

or:

2. Activate the PLLUTMI twice, following the procedure below:

a. Start The UTMI PLL an wait for the PLL lock bit

b. Disable the UTMI PLL and wait 10 µ seconds minimum

c. Restart the UTMI PLL and wait for the PLL Lock bit

Below is a possible implementation of the workaround:

/* First enable the UTMI PLL */

AT91C_BASE_PMC->CKGR_UCKR |= (AT91C_CKGR_UCKR_PLLCOUNT & (0x3 << 20)) |

AT91C_CKGR_UCKR_UPLLEN;

tmp =0;

while (((AT91C_BASE_PMC->PMC_SR & AT91C_PMC_SR_LOCKU) == 0) && (tmp++ <

DELAY));

/* Disable the PLLUTMI and wait 10µs min*/

AT91C_BASE_PMC->CKGR_UCKR &= ~AT91C_CKGR_UCKR_UPLLEN;

tmp = 0;

while(tmp++ < DELAY2); // DELAY2 must be defined to fit the 10 µs min;

/* Re- enable the UTMI PLL and wait for the PLL lock status*/

AT91C_BASE_PMC->CKGR_UCKR |= (AT91C_CKGR_UCKR_PLLCOUNT & (0x3 << 20)) |

AT91C_CKGR_UCKR_UPLLEN;

tmp =0;

while (((AT91C_BASE_PMC->PMC_SR & AT91C_PMC_SR_LOCKU) == 0) && (tmp++ <

DELAY));

SAM9G46 Series [DATASHEET]

Atmel-11028G-ATARM-SAM9G46-Datasheet_08-Dec-15

1259

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