/********************************************************************
	lcd_demo.c			 
	Z-World, 2000			 

	The is a sample program for connecting to an LCD (which uses the
	HD44780 controller, or an equivalent), using the RCM 2100
	external I/O rabbit port.

This is the initialization sequence for a 2 by 20 character LCD
programmed in 8 bit mode:
	delay for power up - allow LCD to reset
	command: 8 bit mode
	command: 2 lines, 5x10 character size, and 8 bit mode again
	command: turn on display and cursor - non blinking
	command: incr address and shift cursor with each character

Note: each command must be followed by a delay to allow the display
to respond.

Connection list: 
Core Module	   LCD
 Signal		  Signal
	D0				DB0
	D1				DB1
	D2				DB2
	D3				DB3
	D4				DB4
	D5				DB5
	D6				DB6
	D7				DB7
	A0				RS		Register Select: 0=command, 1=data
	A1				R/W	0=write, 1=read
	*				E		normally low: latches on high to low transition

* = circuit which uses a 74HC02, or equivalent, as follows

			|----\
/PE0-----O		|	|-----|	|----\
			|		|--|		|	|		|
/IOR-----O		|	|		|	|		|
			|----/	|		|	|		|
						|		O--O		|---- E
			|----\	|		|	|		|
/PE0-----O		|	|		|	|		|
			|		|--|		|	|		|
/IOW-----O		|	|-----|	|----/
			|----/

	Bus address		Function
		0				write command byte
		1				write data byte
		2				read busy flag and address
		3				read data from RAM

	See notes above for power and brightness.

********************************************************************/

/********************************************************************
MsDelay - delay some number of milliseconds
	input parameter: int number of milliseconds to delay
	return value: none
	errors: none
********************************************************************/
void MsDelay ( int iDelay )
{	unsigned long ul0;
	ul0 = MS_TIMER;				// get current timer value
	while ( MS_TIMER < ul0 + (unsigned long) iDelay );
}

/*******************************************************************
UsDelay - delay some number of micro seconds - very approximate!!
	about 11usec per iteration with the 7.3MHz crystal.  The formula
	used here was determined experimentally.
********************************************************************/
void UsDelay ( int iDelay )
{	int i;
	iDelay /= 11;
	for ( i=0; i<iDelay; i++ );
}

#define	WCOMMAND	0
#define	WDATA		1
#define	RBUSY		2	// not currrently used
#define	RRAM		3	// not currrently used

/*********************************************************************
WriteByte - send a byte to the LCD
*******************************************************************/
#asm
;function requires two parameters:
;@sp+2= 1st parameter value = external I/O address
;@sp+4= 2nd parameter value = data
;
;Need to clock doubler in order to meet the set up and hold
;time requirements of the LCD.  For a faster CPU time you may
;need to set the CPU clock to "divide by 8" mode

WriteByte::
			xor	a				;a = 0
	ioi	ld		(GCDR), a	;turn off clock doubler

			ld		hl,(sp+4)	; get data value
			ld		a, l			; save it for ioe
			ld		hl,(sp+2)	; get data address
	ioe	ld		(hl),a		; ship data value

			ld		a, (GCDRShadow)
	ioi	ld		(GCDR), a	;restore clock doubler

			ld		hl, 100		;set up for
			push	hl
			call	UsDelay	;delay
			pop	hl
			ret
#endasm


/*********************************************************************
LCD_Init - Initialize the LCD for the following operating parameters:
	8 bit mode, 2 lines, 5x10
	turn on display and cursor: non-blinking
	incr address and shift cursor with each character
*******************************************************************/
void LCD_Init ()
{
	// set up PE0 as I/O strobe
	WrPortI ( PEDDR, &PEDDRShadow, 1 );	// PE0 = output
	WrPortI ( PEFR, &PEFRShadow, 1 );	// PE0 = I/O strobe
	WrPortI ( IB0CR, NULL, 0x08 );		// permit write, chip select, 15 wait states
	MsDelay ( 1000 );							// wait for LCD to reset itself

	WriteByte ( WCOMMAND, '\B00111100' );	// 8 bit mode
	UsDelay (100);
	WriteByte ( WCOMMAND, '\B00111100' ); 	// 8 bit mode,  2 lines, 5x10
	WriteByte ( WCOMMAND, '\B00001110' );	// turn on display and cursor: non-blinkin
	WriteByte ( WCOMMAND, '\B00000110' );	// incr address and shift cursor with each character
}


/*********************************************************************
Display - display a line of text on the LCD
	argument: address of null terminated text string
*******************************************************************/
void Display ( char *szp )
{
	while ( *szp ) WriteByte ( WDATA, *szp++ );
}

void Clear ( void )
{
	WriteByte ( WCOMMAND, 0x01 );	// clear the display
	MsDelay (3);						// insure at least 2 msec
}

void Line2 ( void )
{
	WriteByte ( WCOMMAND, 0xC0 );	// set RAM address to Line 2
					//note: this value may vary for different displays
	MsDelay (3);						// insure at least 2 msec
}

/********************************************************************/
/********************************************************************/

void main ()
{

	LCD_Init ();
		// IMPORTANT - the initialization sequence should only
		// be executed once after powerup.  Multiple executions
		// will cause the display to malfunction.
	
	while (1) {
		Clear();
		Display ( "0123456789" );
		MsDelay (500);
		Clear();
		Display ( "This is a test!" );
		MsDelay (500);

		Line2 ();
		Display ( "This is line TWO!" );
		MsDelay (500);
		}
}
