HPLL and USART problem

Luciano · Post by **Luciano** » Fri Jul 09, 2010 10:13 am

I am using a PIC 18F4525 with a 20MHz quartz oscillator, and the USART serial transmission at 115200 baud.
everything works fine using the USART library, but if I insert the HPLL to work at 40Mhz the USART stops working.

is there anything else, in addition to the instructions of the manual, that should be modified in order to have the USART working at 40Mhz? or else the USART module just does not work with HPLL?

many thanks
Luciano

CharlieM · Post by **CharlieM** » Fri Jul 09, 2010 11:01 am

What are you setting your xtal to? if you are using a 20 mhz osc and pll then you need to set you xtal to 80.

Jerry Messina · Post by **Jerry Messina** » Fri Jul 09, 2010 12:45 pm

The 4525 is rated for 40MHz operation, and the PLL is 4X, so the max ext crystal freq is 10MHz.

Luciano · Post by **Luciano** » Mon Jul 12, 2010 8:31 am

that clarifies the problem! many thanks
Luciano