/************************************************************************
*									*
*	print_cmd(): This enters a data out phase and transfers a block *
*		     of data to memory using block mode DMA.The size of *
*		     this block has already been determined in 		*
*		     process_cmd() and is known to be within the 	*
*		     allowed limits.					*
*									*
************************************************************************/

print_cmd()
{
	print_on=TRUE;				/* Flag to show print routine that data is available	*/
	if (!previous)				/* The Que must be set up on the first running of the program  */
	{
		top=&buffer[BUFFSZ-1];
		bottom=&buffer[0];
		front=rear=bottom;
		previous=TRUE;
	}
	data2=data_len;
	if (rear > ((top-data_len)+1))		/* Incremented to include location rear	*/
	{
		data1=(top-rear)+1;		/* Incremented to include location rear	*/
		data2=data_len-data1;
		dma_data(data1);
		rear=bottom;
	}
	dma_data(data2);
	rear=rear+data2;
	if (rear > top)	rear=bottom;		/* This is incase the DMA fills the que to the top	*/
}


/************************************************************************
*									*
*	dma_data(data):	This carries out the print commands DMA receive *
*			,transferring 'data' bytes of data to the	*
*			address pointed to by 'rear'.			*
*									*
************************************************************************/

dma_data(data)
int data;
{
	write(DMAMCL,DONT_CARE);
	write(DMAMOD, (BLOCK_MODE | WRITE_TRANSFER));
	write(DMAMSK,CHANNEL0);
	dmawrit(DMAADD,rear);
	dmawrit(DMACNT,--data);		/* DMA controller count is one less than the number of bytes transferred	*/
	write(EASITCR,DATA_OUT);
	write(EASIMR2,BLK_MODE_DMA);
	dma(EASISDT);
}


/************************************************************************
*									*
*	outbuf(): This routine outputs the entire contents of the queue *
*		   to the printer, via port B of the PIO. When the 	*
*		   buffer is empty print_on is set FALSE,to signify 	*
*		   printing is finished.				*
*									*
************************************************************************/

outbuf()
{
	in_print=TRUE;	
	eni();				/* Enable interrupt to allow selection	*/
	while (front != rear)
	{
		printit();
		if (front > top)
			front=bottom;
		if (byt_empty() > BUFFLIM)
			next=TRUE;
		else
			next=FALSE;
		if (recon && (byt_empty() > recon_data))
			reconnect();
	}
	print_on=in_print=FALSE;
	sense[0]=NO_SENSE;
}


/************************************************************************
*									*
*	printit():	This prints out the character at the front of	*
*			the que, returning a zero if successful, a one  *
*			if an error occurs.On error the que is flushed. *
*									*
************************************************************************/


printit()
{
	while (read(PIOB) & PRINTER_ERROR)
	{
		if (!(read(PIOB) & PRINTER_PE))
			sense[0]=MEDIUM_ERROR;
		else
			sense[0]=UNIT_ATTENTION;
		if (recon)
			reconnect();
	}
	while ((!(read(PIOB) & PRINTER_BUSY)) && (!(read(PIOB) & PRINTER_ERROR)));	/* In case of error occurring while */
	if (!(read(PIOB) & PRINTER_ERROR))						/* waiting for busy.		    */
	{
		if (front != rear)		/* Checked in case printer was in an error condition and queue was flushed  */
		{
			write (PIOA,*front++);
			write (PIOC, (PRINTER_STROBE | LED_ON));
			write (PIOC,LED_ON);
		}
	}
}


/************************************************************************
*									*
*	byt_empty():	This returns the number of bytes still to be	*
*			filled in the que.				*
*									*
************************************************************************/

byt_empty()
{
	if (front < rear) return ((top-rear) + (front-bottom));
	if (front > rear) return (front-rear);
	if (front ==rear) return BUFFSZ;
}