/****************************************************************************************************************
ELE3EMP Laboratory 3 - Introduction to ZiLOG Z8Encore Development Environment
- Task 1 -
Blink all four LEDs on the Development Board.  

Written by Daniel Stephenson, 17/2/2006
Modified by Geoffrey Tobin, 7, 15, 22 March 2007
****************************************************************************************************************/

#include <stdio.h>

// A byte is an unsigned 8-bit quantity.
typedef unsigned char byte;

#include <eZ8.h>

// Function Prototypes
void delay (void);
void init_IO (void);
void LED_bit_pattern (byte);
void turn_off_LEDs (void);
void turn_on_LEDs (void);

/****************************************************************************************************************/
/* Main program begins here */
/* This  program blinks ALL 4 LEDs continually */
/****************************************************************************************************************/
void main (void)
{	
	init_IO();					// Initializes PortG[0..3] to drive LEDs
	turn_off_LEDs();			// Make sure the LEDs are off to begin the program
	delay();                // Keep them off for one "unit" of delay

	for(;;)					// Infinite loop
	{
		turn_on_LEDs ();
      // keep LEDs on for three "units" of delay
		delay();
		delay();
		delay();

		turn_off_LEDs ();
      // keep LEDs off for three "units" of delay
		delay();
		delay();
		delay();
	} // end of infinite loop

} // end of main()


/****************************************************************************************************************/
//  function to intiialise PORTG which has the LEDs attached to the lower nibble bits PortG[0..1]
//  requires no input, returns nothing
/****************************************************************************************************************/
void init_IO (void)
{
	//	LEDs and Switches
	PGADDR = 0x02;	// Select Alternate Function Register
	PGCTL = 0x00;	// Select GPIO function
	PGADDR = 0x01;  // select the DDR register
	PGCTL = 0xF0;  	// set DDR reg to set bits 0 to 3 as output, bits 4 to 7 as input
	// note that PGOUT is set to 0x00 by CPU upon reset => outputs will be LOW after the previous line executes
	PGADDR = 0x00;	// Set ADDR register back to 0x00 to prevent further changes
}


/****************************************************************************************************************/
//  Turn ON all LEDs
//  communicates only with the LEDs
//  requires no input, returns nothing
/****************************************************************************************************************/
void turn_on_LEDs (void)
{
	LED_bit_pattern (~0);
}	// end of turn_off_leds()

/****************************************************************************************************************/
//  Turn OFF all LEDs
/****************************************************************************************************************/
void turn_off_LEDs (void)
{
	LED_bit_pattern (0);
}	// end of turn_off_leds()


/****************************************************************************************************************/
//  Place any desired bit pattern on the LEDs: 1 = on, 0 = off
//  requires byte input, returns nothing
/****************************************************************************************************************/
void LED_bit_pattern (byte bit_pattern)
{
	// LED anodes are at the positive supply voltage;
   // LED cathodes are connected as outputs to Port G bits 0 to 3:
   // this makes the LEDs are active low on the board.
   // 0x0F = 0000 1111 in binary.
   // So this bit mask selects the LEDS and only the LEDs.
	enum { LED_bits = 0x0F };

   // The long way: a step-by-step process:
   // Invert bit_pattern to compensate for active LOW controls
   // which occur because PGOUT is connected to the LEDs' cathodes.
   // 	byte led_pattern = ~ bit_pattern;

   // LED-connected bits (LED_bits) of the pattern must be set.
   // 	byte change = led_pattern & LED_bits;

   // Keep other bits (~LED_bits) of Port G data unchanged.
 	// 	byte keep = PGIN & ~LED_bits;

   // Finally, combine the kept bits and the changed bits.
   // 	PGOUT = keep | change;

   //	All of the above, in one line:
	PGOUT = (PGIN & ~LED_bits) | (~bit_pattern & LED_bits);

}	// end of LED_bit_pattern()


/****************************************************************************************************************/
// A fixed, blocking, software delay routine using a nested 'for' loop. 
// For a precise delay, use an internal Z8 TIMER.  (TIMERs are in a later lab.)
// requires no input, returns nothing.
/****************************************************************************************************************/
void delay (void)
{
	int i, j;

   j = 0;
	// waste some CPU time => results in delay
	for (i=0; i < 32000; i++)
	{
		j = j++;
		j = j--;
	}
  	// waste some more time
	for (i=0 ; i < 15000; i++)
   {
   }
}	// end of delay()
//-------------------------------------------------------------------ADD NEW FUNCTIONS SOUTH OF THIS LINE-------