/*
*********************************************************************************************************
* Module     : PRN_IO.C
* Author     : Randy Rasa
* Description: Printer Port I/O Routines
*
* The functions in this module implement a low-level C interface to the standard PC parallel
* printer port, providing up to 12 outputs and 5 inputs.
*
* A standard PC provides for three printer ports, at the following base addresses:
*
*   LPT1 = 0x0378 or 0x03BC
*   LPT2 = 0x0278 or 0x0378
*   LPT3 = 0x0278
*
* This module assumes that LPT1 is at 0x0378.  There's a way to detect this automatically,
* but for simplicity I haven't bothered.  You could also allow an external module to set this
* via a function call, if the port needs to be changed on the fly.
*
* The printer port has three 8-bit registers:
*
*   Data Register (base   0) ........ outputs
*
*     7 6 5 4 3 2 1 0
*     . . . . . . . *  D0 ........... (pin 2), 1=High, 0=Low (true)
*     . . . . . . * .  D1 ........... (pin 3), 1=High, 0=Low (true)
*     . . . . . * . .  D2 ........... (pin 4), 1=High, 0=Low (true)
*     . . . . * . . .  D3 ........... (pin 5), 1=High, 0=Low (true)
*     . . . * . . . .  D4 ........... (pin 6), 1=High, 0=Low (true)
*     . . * . . . . .  D5 ........... (pin 7), 1=High, 0=Low (true)
*     . * . . . . . .  D6 ........... (pin 8), 1=High, 0=Low (true)
*     * . . . . . . .  D7 ........... (pin 9), 1=High, 0=Low (true)
*
*   Status Register (base   1) ...... inputs
*
*     7 6 5 4 3 2 1 0
*     . . . . . * * *  Undefined
*     . . . . * . . .  Error ........ (pin 15), high=1, low=0 (true)
*     . . . * . . . .  Selected ..... (pin 13), high=1, low=0 (true)
*     . . * . . . . .  No paper ..... (pin 12), high=1, low=0 (true)
*     . * . . . . . .  Ack .......... (pin 10), high=1, low=0 (true)
*     * . . . . . . .  Busy ......... (pin 11), high=0, low=1 (inverted)
*
*   Control Register (base   2) ..... outputs
*
*     7 6 5 4 3 2 1 0
*     . . . . . . . *  Strobe ....... (pin 1),  1=low, 0=high (inverted)
*     . . . . . . * .  Auto Feed .... (pin 14), 1=low, 0=high (inverted)
*     . . . . . * . .  Initialize ... (pin 16), 1=high, 0=low (true)
*     . . . . * . . .  Select ....... (pin 17), 1=low, 0=high (inverted)
*     * * * * . . . .  Unused
*
* Pins 18-25 are ground.  You can get fancy, and do some bidirectional transfers with certain
* parallel ports, but this simple structure works for everything I've tried it on.  For more
* information, consult some of the excellent FAQs on the Internet ...
*
* This module maintains shadow buffers for the data and control registers, so that a single
* bit can be changed without disturbing other bits within the same register.  All inputs and
* outputs have a corresponding function to read or write them, using the "official" signal name.
* In addition, the PrnIO_Data() function allows you to write to the entire data register at once,
* which is useful for communicating with byte-wide devices.
*
* The header file provides a number of macros which allow you to refer to the inputs and outputs
* by number, (e.g. PrnIO_In0(), PrnIO_Out0(), etc.).
*
* This module was written for use with Borland C/C   v3.1.  It may be used with other compilers,
* but you'll most likely need to change the inport() and outport() functions to the equivalent
* library functions provided by the other compilers.  You may also need to change the names of the
* header files for other compilers ...
*
*********************************************************************************************************
*/    /*
*********************************************************************************************************
* Include Header Files
*********************************************************************************************************
*/
#include 
#include 
#include 
#include 
#include "prn_io.h"    /*
*********************************************************************************************************
* Constants
*********************************************************************************************************
*/
#define BASE_ADDRESS      0x0378                      // printer port base address
#define DATA_REGISTER     (BASE_ADDRESS 0)            //  address of data register
#define STATUS_REGISTER   (BASE_ADDRESS 1)            //  address of status register
#define CONTROL_REGISTER  (BASE_ADDRESS 2)            //  address of control register    /*
*********************************************************************************************************
* Private Data
*********************************************************************************************************
*/
static unsigned char data_reg;
static unsigned char control_reg;        // ...................................... Public Functions ..............................................    /*
*********************************************************************************************************
* PrnIO_Init()
*
* Description: Initialize module; must be called before any other functions in this module.
* Arguments  : none
* Returns    : none
*********************************************************************************************************
*/
void PrnIO_Init (void)
{
  data_reg = control_reg = 0;                         // clear shadow registers
}    /*
*********************************************************************************************************
* PrnIO_...()
*
* Description: Input and output routines.  These use the actual names of the pins.
*********************************************************************************************************
*/
void PrnIO_D0 (char state)
{
  if (state == 0)
    data_reg &= ~0x01;
  else
    data_reg |=  0x01;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_D1 (char state)
{
  if (state == 0)
    data_reg &= ~0x02;
  else
    data_reg |=  0x02;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_D2 (char state)
{
  if (state == 0)
    data_reg &= ~0x04;
  else
    data_reg |=  0x04;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_D3 (char state)
{
  if (state == 0)
    data_reg &= ~0x08;
  else
    data_reg |=  0x08;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_D4 (char state)
{
  if (state == 0)
    data_reg &= ~0x10;
  else
    data_reg |=  0x10;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_D5 (char state)
{
  if (state == 0)
    data_reg &= ~0x20;
  else
    data_reg |=  0x20;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_D6 (char state)
{
  if (state == 0)
    data_reg &= ~0x40;
  else
    data_reg |=  0x40;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_D7 (char state)
{
  if (state == 0)
    data_reg &= ~0x80;
  else
    data_reg |=  0x80;
  outport(DATA_REGISTER,data_reg);
}    void PrnIO_Data (unsigned char dataout)
{
  data_reg = dataout;
  outport(DATA_REGISTER,data_reg);
}    char PrnIO_Error (void)
{
  if (inport(STATUS_REGISTER) & 0x08)
    return 1;
  else
    return 0;
}    char PrnIO_Selected (void)
{
  if (inport(STATUS_REGISTER) & 0x10)
    return 1;
  else
    return 0;
}    char PrnIO_PaperOut (void)
{
  if (inport(STATUS_REGISTER) & 0x20)
    return 1;
  else
    return 0;
}    char PrnIO_Acknowledge (void)
{
  if (inport(STATUS_REGISTER) & 0x40)
    return 1;
  else
    return 0;
}    char PrnIO_Busy (void)
{
  if (inport(STATUS_REGISTER) & 0x80)
    return 0;
  else
    return 1;
}    void PrnIO_DataStrobe (char state)
{
  if (state == 0)
    control_reg |=  0x01;
  else
    control_reg &= ~0x01;
  outport(CONTROL_REGISTER,control_reg);
}    void PrnIO_Autofeed (char state)
{
  if (state == 0)
    control_reg |=  0x02;
  else
    control_reg &= ~0x02;
  outport(CONTROL_REGISTER,control_reg);
}    void PrnIO_InitOut (char state)
{
  if (state == 0)
    control_reg &= ~0x04;
  else
    control_reg |=  0x04;
  outport(CONTROL_REGISTER,control_reg);
}    void PrnIO_Select (char state)
{
  if (state == 0)
    control_reg |=  0x08;
  else
    control_reg &= ~0x08;
  outport(CONTROL_REGISTER,control_reg);
}    /*
*********************************************************************************************************
* Module     : PRN_IO.H
* Author     : Randy Rasa
* Description: Header file for PRN_IO.C (Printer Port I/O Routines)
*********************************************************************************************************
*/    /*
*********************************************************************************************************
* Public Function Prototypes
*********************************************************************************************************
*/
void PrnIO_Init (void);
void PrnIO_D0 (char state);
void PrnIO_D1 (char state);
void PrnIO_D2 (char state);
void PrnIO_D3 (char state);
void PrnIO_D4 (char state);
void PrnIO_D5 (char state);
void PrnIO_D6 (char state);
void PrnIO_D7 (char state);
void PrnIO_Data (unsigned char dataout);
char PrnIO_Error (void);
char PrnIO_Selected (void);
char PrnIO_PaperOut (void);
char PrnIO_Acknowledge (void);
char PrnIO_Busy (void);
void PrnIO_DataStrobe (char state);
void PrnIO_Autofeed (char state);
void PrnIO_InitOut (char state);
void PrnIO_Select (char state);    /*
*********************************************************************************************************
* Macros
*********************************************************************************************************
*/
#define PrnIO_In0()     PrnIO_Error()
#define PrnIO_In1()     PrnIO_Selected()
#define PrnIO_In2()     PrnIO_PaperOut()
#define PrnIO_In3()     PrnIO_Acknowledge()
#define PrnIO_In4()     PrnIO_Busy()    #define PrnIO_Out0(x)   PrnIO_D0(x)
#define PrnIO_Out1(x)   PrnIO_D1(x)
#define PrnIO_Out2(x)   PrnIO_D2(x)
#define PrnIO_Out3(x)   PrnIO_D3(x)
#define PrnIO_Out4(x)   PrnIO_D4(x)
#define PrnIO_Out5(x)   PrnIO_D5(x)
#define PrnIO_Out6(x)   PrnIO_D6(x)
#define PrnIO_Out7(x)   PrnIO_D7(x)
#define PrnIO_Out8(x)   PrnIO_DataStrobe(x)
#define PrnIO_Out9(x)   PrnIO_Autofeed(x)
#define PrnIO_Out10(x)  PrnIO_InitOut(x)
#define PrnIO_Out11(x)  PrnIO_Select(x)    

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