A 12F675 is used with internal oscillator. A led is connected to Vdd and GP4 with a resistor, a 0,1u capacitor is the only other component. This code works with CCS C (http://www.ccsinfo.com/picc.shtml). #include <12F675.h> #device ADC=10 #fuses INTRC_IO,NOWDT,NOPUT,NOPROTECT,NOCPD,NOMCLR #use delay(clock=4000000) #define GP0 PIN_A0 #define GP1 PIN_A1 #define GP2 PIN_A2 #define GP3 PIN_A3 #define GP4 PIN_A4 #define GP5 PIN_A5 #byte OSCCAL = 0x80 void init() { OSCCAL = 0x80; // set internal oscillator to mid frequency set_tris_a( 0b11111101 ); // set GP1 output, all other inputs setup_comparator( NC_NC_NC_NC ); // disable comparators setup_adc_ports( NO_ANALOGS ); // disable analog inputs setup_adc( ADC_OFF ); // disable A2D } main() { init(); while ( TRUE ) // blink LED { output_high( GP4 ); // turn LED on delay_ms( 250 ); // wait 250ms output_low( GP4 ); // turn LED off delay_ms( 250 ); // wait 250ms } }