/******************************************************************************
*
* project name: TICT Tutorial Series 1 - PART II
* file name:    timer1.c
* initial date: 31/10/2000
* author:       thomas.nussbaumer@gmx.net
* description:  simple counter example using an own interrupt handling routine
*
* build this program by typing: tigcc -O2 timer1.c
*
*
* $Id: timer1.c,v 1.1 2000/11/01 10:44:46 Thomas Nussbaumer Exp $
*
******************************************************************************/

#define SAVE_SCREEN

#include <tigcclib.h>

int _ti89, _ti92plus;  // produce code for TI89 and TI92plus

INT_HANDLER oldint5 = NULL;

//-------------------------------------------------------------
// NOTE that variable counter is defined "volatile" !!!
//
// "volatile" means that the compiler shouldn't touch it in any
// way for optimization reasons.
//
// if this variable is not defined "volatile" the compiler
// may completely remove it, because it thinks it will change
// during routine (the compiler doesn't know anything about
// interrupts, so this may fool it).
//-------------------------------------------------------------
volatile int counter = 0;


DEFINE_INT_HANDLER (myint5handler) {
    counter++;
    //-----------------------------------------------------
    // we don't want to replace the old interrupt handler
    // completely, but want that it will be executed at the
    // end of our own handler
    //-----------------------------------------------------
    ExecuteHandler(oldint5);
}


void _main(void) {
    //-------------------------------------------------------
    // clear screen and set counter variable to 0, otherwise
    // the counter would start at its last value if you start
    // the program again and the program is not archived!
    //-------------------------------------------------------
    ClrScr();
    counter = 0;

    //---------------------------------------------------
    // get the address of the default interrupt 5 handler
    // and store it in the global variable oldint5.
    // this is necessary so we can call this handler within
    // our own handler and that we can restore it at the
    // end of our program
    //---------------------------------------------------
    oldint5 = GetIntVec(AUTO_INT_5);

    //--------------------------------------
    // install now our own handler ....
    //--------------------------------------
    SetIntVec(AUTO_INT_5, myint5handler);

    //------------------------------------------------------------------
    // ... loop and print the counter value until a key gets pressed ...
    //------------------------------------------------------------------
    while (!kbhit()) {
        if (TI89) printf_xy(50, 50, "Counter=%d  ", counter);
        else      printf_xy(70, 64, "Counter=%d  ", counter);
    }

    //----------------------------------------------------------
    // install the previous handler again (removing our own one)
    //----------------------------------------------------------
    SetIntVec(AUTO_INT_5, oldint5);

    //-------------------------------------------------------
    // empty the keyboard buffer and return.
    // its a really good idea to empty the keyboard buffer
    // and this point. otherwise the pressed key will remain
    // in the buffer and will be handed over to the AMS.
    // if the pressed key is the [ENTER] key you program
    // would get started immediately again.
    //-------------------------------------------------------
    GKeyFlush();
}

//=============================================================================
// Revision History
//=============================================================================
//
// $Log: timer1.c,v $
// Revision 1.1  2000/11/01 10:44:46  Thomas Nussbaumer
// initial version
//
//
//