PIC16F819 LED not blinking

[Bruce]

Your config options have ZERO effect on actual config settings.

@__Config_INTRC_OSC 
@__Config_PWRT_OFF
@__Config_MCLR_OFF
@__Config_BOREN_OFF
@__Config_DEBUG_OFF

So your config settings are whatever the default config options are set to in your
PBP 16F819.INC file for the MPASM assembler.

And, like Melanie mentioned, you for sure will want the WDT disabled since DEFINE OSC 3
is for a 3MHz osc & not 32kHz osc, so your timing is way off.

Try this just to verify it's working;

DEFINE OSC 4 
@ __CONFIG _INTRC_IO & _WDT_OFF & _PWRTE_OFF & _LVP_OFF & _MCLR_OFF & _BODEN_OFF & _DEBUG_OFF
OSCCON = %01100000  ' 4MHz 
ADCON1=7 
TRISA = %00000000 
TRISB = %00000000 
TRISB.4 = 0 
TRISA.0 = 0 
PORTA.0 = 0 
PORTB.4 = 0 

LOOP: 

PULSOUT PORTB.4,20 
PAUSE 20
PULSOUT PORTA.0,20 
PAUSE 20 

Goto LOOP

And, for PBP 2.6 you'll want to change LOOP to something like LOOPS since LOOP is now a
reserved word.