//---------------------------------------------------------------
// L313.C
// Using the 80C188XL Internal Timer.
//
// C Code for the SBC188 Board.
// C.P. Diduch, Dec 1999.
//---------------------------------------------------------------
#define	KEY_PA 	0x138	  // 82C55A port addresses for PA,
#define KEY_PB 	0x13A	  // PB,
#define KEY_PC 	0x13C	  // PC and the
#define KEY_CON	0x13E	  // Control Register.
//---------------------------------------------------------------
// Details of the 80C188XL timer-counter unit can be found 
// on pages 9-1 though 9-23 of the Intel 80C186/80C188XL 
// Users Manual available in the lab and online at:
// http://developer.intel.com/design/intarch/manuals/

#define	T1CNT	0xFF58	  // 80C188 TIMER1 count register.
#define T2CNT	0xFF60	  // 80C188 TIMER2 count register.
#define T1CON	0xFF5E	  // 80C188 TIMER1 control register.
#define T2CON	0xFF66	  // 80C188 TIMER2 control register.
#define T1CMPA	0xFF5A	  // 80C188 TIMER1 maximum count register.
#define T2CMPA	0xFF62	  // 80C188 TIMER2 maximum count register.

#include <conio.h> 	  // conio.h contains prototypes for 
			  // inportb() and outportb(). 
			
void TIMER_INIT(void);	  // Function declarations (prototypes).
void PPI_INIT(void);
//---------------------------------------------------------------
void main()
{
unsigned time;
unsigned char C;

PPI_INIT();
do {
   TIMER_INIT();
   do {
      time = inport(T1CNT);
      }
   while (time <= 50000);
   C = C + 1;
   outportb(KEY_PC, C);
   }
while (C < 255);
}
//---------------------------------------------------------------
void PPI_INIT(void)
{
outportb(KEY_CON, 0x82);  // Initialize KEY_PC and KEY_PA
}                      	  // as OP ports and KEY_PB as IP.
//---------------------------------------------------------------
void TIMER_INIT(void)
{
outport(T2CNT, 0);	  // Clear timer count registers 
outport(T1CNT, 0);	  // before programming mode.
outport(T2CMPA, 4);	  // Timer2 is clocked at 4 MHz / 4
			  // causing a time-out once every
			  // microsecond. Each time-out on 
outport(T1CMPA, 0xFFFF);  // timer2 triggers timer1. 
			  // T1CMPA is set to MAX.
outport(T2CON, 0xC001);	  // Enable Timer2 for continuous mode.
outport(T1CON, 0xC009);	  // Enable Timer1 for continous mode and
			  // internally clocked by a time-out on
}  			  // Timer 2.
//---------------------------------------------------------------