mnpdrvr.c

汇编源代码大全2

** of the real pointer.
*/
	case RF_INFOL:
		if ((rcv_char != DLE) || ((rcv_char == DLE) && rdle_flg))
			{
	    		if ((rcv_char == ETX) && rdle_flg) 
				{
				fcscalc(&rcv_fcs, rcv_char);
				rf_state = RF_FCS1;
				}
	    		else
				{
				rdle_flg = 0;
                	rf_tiptr = rb_iptr; 		
	        		put_char();
				rf_state++; 		   
				}
			}
		else
	    		rdle_flg = 1;
		break;

/* State RF_INFO - Receive data bytes until the stop flag is found.
*/
	case RF_INFO:
		if ((rcv_char != DLE) || ((rcv_char == DLE) && rdle_flg))
			{
	    		if ((rcv_char == ETX) && rdle_flg)
				{
				fcscalc(&rcv_fcs, rcv_char);
				rf_state++;		
				}
	    		else
				put_char();
	    		rdle_flg = 0;
	    		}
		else
	    		rdle_flg = 1;
		break;

/* State RF_FCS1 - Receive first byte of fcs.
*/
	case RF_FCS1:
		rfcs.hi = rcv_char;
		rf_state++;
		break;

/* State RF_FCS2 - Receive second (low) byte of fcs and take end-of-
** frame action.  If the calculated fcs is not identical to that
** received, the received frame is "broken".  Signal this to the sender
** by setting the LPDU type to 0 and setting the FORCE_ACK flag.  If the
** FCS's match, take action based on the type of LPDU received. 
*/
	case RF_FCS2:
		if ((rcv_fcs.hi != rfcs.hi) || (rcv_fcs.low != rcv_char))
			{
	    		lcb.lpdu_type = 0;
	    		SETBIT2(FORCE_ACK);
	    		ret_b(&rlkb, hdr_struct);
	    		}
		else
			{
	    		switch (lcb.lpdu_type = *(hdr_struct->bptr + PDU_TYPE))
				{
				case LT:
		    			rcv_lt();
		    			break;

				case LA:
		    			rcv_la();
		    			break;

/* Link Request - If an LR arrives during what we think is the data
** phase, the other side may be retransmitting. In this case, just
** discard the LR.  Otherwise, save the LR for the mainline to process.
** In either case, signal the mainline to ack. 
*/
				case LR:
		    			if (BIT1SET(LINK_EST))
						ret_b(&rlkb, hdr_struct);
		    			else
						rlkb.used_lst = hdr_struct;  
		    			SETBIT2(FORCE_ACK)
		    			break;

				case LN:
		    			rcv_ln();
		    			break;

				case LNA:
		    			rcv_lna();
		    			break;

/* Link Disconnect - Signal link termination to the mainline.  If the LD
** contains a user reason byte (signalled by parm 1 having a value of
** 255), save it in the LCB. 
*/
				case LD:
		    			CLRBIT1(LINK_EST)
		    			if (*(hdr_struct->bptr + 4) == 255)
						{
						p_mnpcb->ld_source = 1;
						p_mnpcb->ld_reason = 
							*(hdr_struct->bptr+7);
						}
		    			else
						p_mnpcb->ld_source = 0;
		    			break;
				}
	    		}

/* Signal the mainline that a frame has been received and reset the
** receive frame state machine for the next frame. 
*/
	    		frame_rcvd = 1;			
	    		rf_state = RF_INIT; 	
	    		break;
		}

}

/*LOCAL----------------------------------------------------------------

	rcv_la - process a received LA LPDU

---------------------------------------------------------------------*/

void rcv_la()
{

register USIGN_8 *p;
USIGN_16 i;
USIGN_8 lt_ret_seq;

/* Ignore this LA LPDU if a destructive attention is in progress. 
*/
if (BIT3SET(LN_SENT))
	{
	ret_b(&rlkb,hdr_struct);
    	return;
    	}

/* For reasons of robustness, check the validity of the LA LPDU 
*/
p = hdr_struct->bptr + 2;			/* point to parm 1 */
if ((*p++ != 1) || (*p != 1))
	{
	ret_b(&rlkb,hdr_struct);
	return;
	}
p += 2;
if ((*p++ != 2) || (*p != 1))
	{
	ret_b(&rlkb,hdr_struct);
	return;
	}

/* If the receive sequence number of this LA is the same as the last
** one received, it may be an implied negative acknowledgment.  Force
** the mainline to consider retransmission by setting the 'force
** retransmission' flag.  Otherwise, save the new number as the last
** acked and set the 'good ack received' flag. 
*/
p -= 2;
if (*p == lcb.ltssn_acked)
	SETBIT2(FORCE_RET)
else
	{
	lcb.ltssn_acked = *p;
    	SETBIT1(LA_RECEIVED)
    	}

/* Process the new credit information received. If it is zero, return.
*/
p += 3;
if ((lcb.rem_credit = *p) == 0)
	{
	ret_b(&rlkb,hdr_struct);
    	return;
    	}

/* If credit is not zero and this ack was a good one, take into account
** the LT LPDUs that may have been sent since the correspondent sent
** this LA.  That is, subtract from the credit the number of these not
** yet acked LTs. 
*/
if (BIT1SET(LA_RECEIVED) && tbcnt)
	{
	lt_ret_seq = *(ftb.used_lst->bptr + LT_SEQ);

	if (lt_ret_seq <= lcb.ltssn_acked)
		i = (lcb.ltssn_acked - lt_ret_seq) + 1;
	else
		i = (256 - lt_ret_seq) + lcb.ltssn_acked + 1;

    	i = tbcnt - i;
    	if (lcb.rem_credit >= i)
		{
		lcb.rem_credit -= i;
        	if (lcb.rem_credit < 0)
			lcb.rem_credit = 0;
        	}
    	else
		lcb.rem_credit = 0;
    	}

/* Clean up 
*/
ret_b(&rlkb, hdr_struct);

}

/*LOCAL----------------------------------------------------------------

	rcv_ln - process a received LN LPDU

---------------------------------------------------------------------*/

void rcv_ln()
{

register USIGN_8 *p;

/* Check the sequence number of this LN LPDU.  If it is the next one
** in the sequence space, signal its arrival to the sender by
** setting the LN_RECEIVED flag.  Also remember the type of the LN LPDU
** by saving the type parameter value in the LCB. 
*/
p = hdr_struct->bptr + 4;
if (*p == (USIGN_8) ++lcb.ln_rsn)
	{
	lcb.ln_rtype = *(p + 3);
    	SETBIT3(LN_RECEIVED)
    	}

/* If this is not the next one, then decrement the receive sequence
** number which was incremented above and signal the need to send an
** LNA LPDU.
*/
else
	{
	lcb.ln_rsn--;
	SETBIT3(FORCE_LNA)
	}

ret_b(&rlkb, hdr_struct);
}

/*LOCAL----------------------------------------------------------------

	rcv_lna -  process a received LNA LPDU

---------------------------------------------------------------------*/

void rcv_lna()
{

register USIGN_8 *p;

/* If the LNA LPDU is an acknowledgment of an outstanding LN, its
** sequence number will match that of the last LN sent.	In this
** case, signal the sender that the LN has been acknowledged.  
** Otherwise, just ignore this LPDU. 
*/
if (*(hdr_struct->bptr + 4) == lcb.ln_ssn)
	{
	lcb.ln_ret_cnt = NULL;
	CLRBIT3(LN_SENT)
	CLRBIT3(LN_TIMER)
	ln_tm=NULL;	
	}
ret_b(&rlkb, hdr_struct);
}

/*LOCAL----------------------------------------------------------------

	rcv_lt - process a received LT LPDU

---------------------------------------------------------------------*/

void rcv_lt()
{

/* Ignore this LT LPDU if a destructive attention is in progress. 
*/
if (BIT3SET(LN_SENT))
	{
	ret_b(&rlkb, hdr_struct);
    	return;
    	}

/* Reset window timer, if window timer is enabled. 
*/
if (BIT2SET(WNDW_TIMER))
	fcw_tm = lcb.window_tmr;

/* Accept this LT LPDU if it is the next one in the sequence space
** and there is room for it (i.e. there is a receive credit).
*/
if ((lcb.lcl_credit > 0)
	 && (*(hdr_struct->bptr + LT_SEQ) == (USIGN_8) lcb.lt_rsn + 1))
	{ 
	++lcb.lt_rsn;
	--lcb.lcl_credit;
	CLRBIT3(DUP_IGNORED)
    	rb_iptr = rf_tiptr;	
    	rb_cnt = rb_cnt + rf_datlen;
    	}

/* Otherwise, ignore the LT LPDU. In this case, set the FORCE_ACK flag
** to get the sender to ack as rapidly as possible.
*/
else
	{
    	SETBIT2(FORCE_ACK)

/* If the LT LPDU is the same as the last one which arrived, i.e. it is
** an immediate duplicate, and this is the first occurrence of the
** immediate duplicate, then don't force the sender to ack this time. 
*/
	if ((*(hdr_struct->bptr + LT_SEQ) == lcb.lt_rsn)
		&& !BIT3SET(DUP_IGNORED))
		{
		CLRBIT2(FORCE_ACK)
		SETBIT3(DUP_IGNORED)		
		}
    	}

/* Clean up 
*/
ret_b(&rlkb, hdr_struct);
}

/*LOCAL----------------------------------------------------------------

	snd_framer - handle a transmit holding register empty
		        interrupt.  This subroutine sends a byte-mode frame.

---------------------------------------------------------------------*/

void snd_framer()
{

extern USIGN_16 port_add;

/* Take action based on the current state of the framer state machine. 
*/
switch (sf_state)
	{

/* State SF_INIT - initial state.  If the mainline has designated an
** LPDU to frame, the sf_busy flag will be true.  If this is the case,
** begin the start flag of the frame. 
*/
    case SF_INIT:
	if (sf_busy)
		{
		snd_char = SYN;
		sf_state++;
		break;
		}
	else
		{
		frame_dne = 1;
		modem_out_busy = 0;
		return;
		}

/* State SF_DLE - Send DLE of start flag. 
*/
	case SF_DLE:
		snd_fcs.hi = snd_fcs.low = 0;
		snd_char = DLE;
		sf_state++;				
		break;

/* State SF_STX - Send STX of start flag. 
*/
	case SF_STX:
		snd_char = STX;
		sf_state++;
		break;

/* State SF_INFO -  As long as there are info field bytes, send a 
** byte and double DLE's as necessary.  At the end of the information
** field of the frame, start the end flag.   Signal the mainline code
** that it can enqueue another frame if it is already waiting on
** 'frame_snt'.  Clearing 'sf_busy' will cause the framer to stop after
** the end flag unless another frame has been enqueued. 
*/
	case SF_INFO:
		if (sf_len > 0)
			{
			if ((snd_char = get_char()) == DLE)
			sf_state++;
			fcscalc(&snd_fcs, snd_char);
			}
		else
			{
			sf_busy = sf_lt = 0;
			frame_snt = 1;
			snd_char = DLE;
			sf_state = SF_ETX;
			}
		break;

/* State SF_DLEINFO - Double an info field DLE.
*/
	case SF_DLEINFO:
		snd_char = DLE;
		sf_state--;
		break;

/* State SF_ETX - Send ETX of end flag.
*/
	case SF_ETX:
		snd_char = ETX;
		fcscalc(&snd_fcs, snd_char);
		sf_state++;
		break;

/* State SF_FCS1 - Send first byte of frame check sequence.
*/
	case SF_FCS1:
		snd_char = snd_fcs.hi;
		sf_state++;
		break;

/* State SF_FCS2 - Send second byte of frame check sequence.
** After this byte is sent, the send framer goes back to its
** initial state.
*/
	case SF_FCS2:
		snd_char = snd_fcs.low;
		sf_state = SF_INIT;
		break;
	}

/* Send byte out RS-232 port 
*/
outp(port_add, snd_char);

}