4MHz to 48MHz for USB at STR711

[shangdawei1]

Posted on October 10, 2005 at 06:12

4MHz to 48MHz for USB at STR711

[shangdawei1]

Posted on October 10, 2005 at 03:09

see:

http://www.olimex.com/dev/pdf/str-p711.pdf Only 4MHz in sch for CK, and I can not find 48 MHz for USBCLK(P1.10). USBCLK(P1.10) is used to check SD card. 4MHz Clock to HCLK(P1.13) for HDLC. can HCLK uses as USB clock? if it can , how can i setup ?

[ben2]

Posted on October 10, 2005 at 04:56

yes you can feed 4Mhz into the HCLK and use this for the USB clock. This is what I am doing. You just need to setup PLL2CR register.

/* setup clock */ PCU->PLL2CR = 0x0050; /* x12 /1 */ while( (PCU->PLL2CR & 0x8000) == 0) { /* wait for pll to lock */ asm(''nop''); }; PCU->PLL2CR |= 0x0180; /* enable pll output and to use as usb clock */ Doing this means the HDLC and USB share the same clock.

[shangdawei1]

Posted on October 10, 2005 at 06:12

Quote:

On 10-10-2005 at 08:26, Anonymous wrote: yes you can feed 4Mhz into the HCLK and use this for the USB clock. This is what I am doing. You just need to setup PLL2CR register. /* setup clock */ PCU->PLL2CR = 0x0050; /* x12 /1 */ while( (PCU->PLL2CR & 0x8000) == 0) { /* wait for pll to lock */ asm(''nop''); }; PCU->PLL2CR |= 0x0180; /* enable pll output and to use as usb clock */ Doing this means the HDLC and USB share the same clock. Thanks, i understand now