(*
 * Copyright 1987, 1989 Samuel H. Smith;  All rights reserved
 *
 * This is a component of the ProDoor System.
 * Do not distribute modified versions without my permission.
 * Do not remove or alter this notice or any other copyright notice.
 * If you use this in your own program you must distribute source code.
 * Do not use any of this in a commercial product.
 *
 *)

const
   carrier_lost = #$E3;              (* code returned with carrier is lost *)

   com_current_chan: integer = 0;    (* current communication channel *)

   port_base:    integer = -1;  (* base port number for 8250 chip *)
                                (* value = -1 until init is finished *)

   port_irq:     integer = -1;  (* port irq number *)

   old_vector:   pointer = nil; (* pointer to original com interrupt handler *)
   
   XOFF_char:    char = ^S;     (* XOFF character code *)

   disable_cts_check: boolean = false; {false if RTS handshake is needed}
   even_parity:   boolean = false; {strip parity?}



var
   port_intr:    integer;       (* interrupt number for 8250 chip *)
   intr_mask:    integer;       (* interrupt controller initialization code *)

   prev_LCR:     integer;       (* previous LCR contents *)
   prev_IER:     integer;       (* previous IER contents *)
   prev_MCR:     integer;       (* previous MCR contents *)
   prev_ICTL:    integer;       (* previous ICTL contents *)

   xmit_active:  boolean;       (* is the transmitter active now?
                                   (is a THRE interrupt expected?) *)

   XOFF_active:  boolean;       (* has XOFF suspended transmit? *)

   rxque:        queue_rec;     (* receive data queue *)
   txque:        queue_rec;     (* transmit data queue *)

   reg:          registers;     (* register package *)

   bios_bastab:  array[0..3] of word absolute $40:0;
                                (* bios table of com port bases for each
                                   port com1..com4 *)


(*
 * Uart register definitions
 *
 *)

const
   ICTL = $21;                  (* system interrupt controller i/o port *)

   RBR = 0;  (* receive buffer register *)
   THR = 0;  (* transmit holding register *)

   DLM = 1;  (* divisor latch MSB *)
   IER = 1;  (* interrupt enable register *)
      IER_DAV     = $01;       (* data available interrupt *)
      IER_THRE    = $02;       (* THR empty interrupt *)
      IER_LSRC    = $04;       (* line status change interrupt *)
      IER_MSR     = $08;       (* modem status interrupt *)


   IIR = 2;  (* interrupt identification register *)
      IIR_PENDING = $01;       (* low when interrupt pending *)

      IIR_MASK    = $06;       (* mask for interrupt identification *)
        IIR_MSR     = $00;       (* modem status change interrupt *)
        IIR_THRE    = $02;       (* transmit holding reg empty interrupt *)
        IIR_DAV     = $04;       (* data available interrupt *)
        IIR_LSR     = $06;       (* line status change interrupt *)


   LCR = 3;  (* line control register *)
      LCR_5BITS   = $00;       (* 5 data bits *)
      LCR_7BITS   = $02;       (* 7 data bits *)
      LCR_8BITS   = $03;       (* 8 data bits *)

      LCR_1STOP   = $00;       (* 1 stop bit *)
      LCR_2STOP   = $04;       (* 2 stop bits *)

      LCR_NPARITY = $00;       (* no parity *)
      LCR_EPARITY = $38;       (* even parity *)

      LCR_NOBREAK = $00;       (* break disabled *)
      LCR_BREAK   = $40;       (* break enabled *)

     {LCR_NORMAL  = $00;}      (* normal *)
      LCR_ABDL    = $80;       (* address baud divisor latch *)


   MCR = 4;  (* modem control register *)
      MCR_DTR     = $01;       (* active DTR *)
      MCR_RTS     = $02;       (* active RTS *)
      MCR_OUT1    = $04;       (* enable OUT1 *)
      MCR_OUT2    = $08;       (* enable OUT2 -- COM INTERRUPT ENABLE *)
      MCR_LOOP    = $10;       (* loopback mode *)


   LSR = 5;  (* line status register *)
     LSR_DAV      = $01;       (* data available *)
     LSR_OERR     = $02;       (* overrun error *)
     LSR_PERR     = $04;       (* parity error *)
     LSR_FERR     = $08;       (* framing error *)
     LSR_BREAK    = $10;       (* break received *)
     LSR_THRE     = $20;       (* THR empty *)
     LSR_TSRE     = $40;       (* transmit shift register empty *)

     LOERR_count:       integer = 0;    {overrun error count}
     LPERR_count:       integer = 0;    {parity error count}
     LFERR_count:       integer = 0;    {framing error count}
     LBREAK_count:      integer = 0;    {break received count}


   MSR = 6;  (* modem status register *)
     MSR_DCTS     = $01;       (* delta CTS *)
     MSR_DDSR     = $02;       (* delta DSR *)
     MSR_DRING    = $04;       (* delta ring *)
     MSR_DRLSD    = $08;       (* delta receive line signal detect *)
     MSR_CTS      = $10;       (* clear to send *)
     MSR_DSR      = $20;       (* data set ready *)
     MSR_RING     = $40;       (* ring detect *)
     MSR_RLSD     = $80;       (* receive line signal detect *)


   COM_BASE_TABLE: ARRAY[0..2] OF WORD = ($3F8,$2F8,$3E8);
   COM_IRQ_TABLE:  ARRAY[0..2] OF BYTE = (4, 3, 4);

   IRQ_MASK_TABLE: ARRAY[0..7] OF BYTE = ($01,$02,$04,$08,$10,$20,$40,$80);
   IRQ_VECT_TABLE: ARRAY[0..7] OF BYTE = ($08,$09,$0A,$0B,$0C,$0D,$0E,$0F);


procedure disable_int;
   inline($FA);

procedure enable_int;
   inline($FB);

procedure io_delay;
   inline($EB/$00);     {jmp $+2}

procedure INTR_service_transmit;
procedure INTR_poll_transmit;
procedure INTR_service_receive;
procedure INTR_check_interrupts;

procedure cancel_xoff;
procedure control_k;
procedure INTR_lower_dtr;
procedure INTR_raise_dtr;
procedure INTR_select_port(chan: integer);
procedure INTR_init_com(chan: integer);
procedure INTR_uninit_com;
procedure INTR_set_baud_rate(speed: word);

procedure INTR_flush_com;
procedure INTR_transmit_data(s:    longstring);
function  INTR_receive_ready: boolean;
function  INTR_receive_data:  char;
procedure verify_txque_space;