18f2520 internal oscillator 16mhz pll enabled rs232

Guest · Posted: Mon Sep 05, 2005 8:25 am

i have problem with an 18f2520 running at 16mhz, the rs232 doesn't work

#include <18F2520.h>
#device adc=8
#fuses HS,NOWDT,NOMCLR,INTRC_IO,NOLVP,NOPBADEN,NOBROWNOUT
#use delay(clock=16000000)
#use rs232(baud=38400,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=9)

oscilator setup:

#asm
MOVLW 0x60
MOVWF 0xFD3
MOVLW 0b11000000
MOVWF 0xF9B
#endasm

the rs232 does not work at all, however the pic boots and apparantle is running at 16mhz.

what to do?

StuartH · Joined: 19 Aug 2005 Posts: 14 Location: W. Midlands, UK

Thw 2520/4520 series has some silicon problems. I suggest you read the Silicon Errata document available on the Microchip website to see if any of the information is applicable to you.

As you seem to be using 9 bit mode, you might well be running into one of the documented issues. Check.

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

From the manual

Ttelmah · Guest

You need to read the data sheet. The PLL, when used with the internal oscillator, _is not_ configured by the fuses, but by setting the PLLEN bit, once the code is running.
So setup the fuses like:
#include <18F2520.h>
#device adc=8
#fuses NOWDT,NOMCLR,INTRC_IO,NOLVP,NOPBADEN,NOBROWNOUT
#use delay(clock=16000000)
#use rs232(baud=38400,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=9)

Then at the start of the code, have:
setup_oscillator(OSC_4MHz | OSC_PLL_ON);

Best Wishes