#include <targets/AT91SAM7.h>

#define LCD_BCK (1<<20)
#define BCK_ON PIOB_ODSR |= LCD_BCK;
#define BCK_OFF PIOB_ODSR &= ~LCD_BCK;
#define BCK_NEG_STATE PIOB_ODSR ^= LCD_BCK;


void init(void){
  PMC_PCER |= PMC_PCER_PIOB | PMC_PCER_TC0;// enable PIOB TIM0
  PIOB_PER |= LCD_BCK;  // pin enable
  PIOB_OER |= LCD_BCK;  // as output
  PIOB_OWER|= LCD_BCK;  // force set

  TC0_CCR = TC0_CCR_CLKDIS;// disable timer0
  TC0_CMR=(1<<2);       // pescaler 1024
  (void)TC0_SR;         // reset ovf flag

  TC0_IDR = 0xFF;       // disable interrupths
  TC0_CCR = TC0_CCR_CLKEN|TC0_CCR_SWTRG; // start and reset timer
}


int main(void){
  init();

  while(1){
    if(TC0_SR&TC0_SR_COVFS)BCK_NEG_STATE;
  }
}