//------------------------------------------------------------------------------------
// Blinky.c
//------------------------------------------------------------------------------------
//
// This program flashes the green LED on the C8051F330 target board about 
// 5x a sec using the interrupt handler for Timer3.
//
// Target: C8051F330
//
//    (based on AN198)
//
// Date: 2009-02-04
//
// Tool chain: SDCC 'c'
//
// Release 1.0
//------------------------------------------------------------------------------------
// Includes
//------------------------------------------------------------------------------------
#include <C8051F330.h>                 // SFR declarations

//------------------------------------------------------------------------------------
// Global CONSTANTS
//------------------------------------------------------------------------------------
#define SYSCLK 2000000  // approximate SYSCLK frequency in Hz
sbit at 0x93 LED;       // p1.3 F330 green LED: '1' = OFF; '0' = ON
#define BLINK_RATE  5              // Min blink rate in Hz for Timer mode

//------------------------------------------------------------------------------------
// Function PROTOTYPES
//------------------------------------------------------------------------------------
char _sdcc_external_startup(void);
void PORT_Init(void);
void Timer3_Init(void);
void Timer3_ISR(void) interrupt 14;

//-----------------------------------------------------------------------------
// Global Variables
//-----------------------------------------------------------------------------
long Num_LED_Flashes = 0;              // Simply counts the number of times
                                       // the LED blinks

//------------------------------------------------------------------------------------
// MAIN Routine
//------------------------------------------------------------------------------------
void
main (void)
{
   PORT_Init();
   Timer3_Init();                  // Init Timer3 to generate interrupts
   EA = 1;                         // enable global interrupts
   while (1) {                     // spin forever
   }
}

//-----------------------------------------------------------------------------
// SDCC special - stop the Watchdog timer prior to initialization
//
// !!! to work properly this requires prototype define (see above)
//-----------------------------------------------------------------------------
char _sdcc_external_startup(void)
{
   // disable watchdog on F330
   PCA0MD &= ~0x40;           // WDTE = 0 (clear watchdog timer enable)
   return 0; // do not skip variable initialization
}

//------------------------------------------------------------------------------------
// PORT_Init
//------------------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports
//
void
PORT_Init (void)
{
   P1MDOUT   = 0x08;       // P1.3 is push-pull
   XBR1      = 0x40;       // Enable Crossbar; pull-ups enabled
}

//-----------------------------------------------------------------------------
// TIMER3_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// Configure Timer3 to 16-bit auto-reload and generate an interrupt at
// interval specified by <counts> using SYSCLK/12 as its time base.
//
// Initially sets Timer3 to overflow at the maximum blink rate.
// The Timer3 ISR is used to toggle the LED.
//
//-----------------------------------------------------------------------------
void
Timer3_Init(void)
{
   TMR3CN  = 0x00;                     // Stop Timer3; Clear flags;
                                       // use SYSCLK/12 as timebase
   CKCON  &= ~0xC0;                    // Timer3 clocked based on T3XCLK;
   TMR3RL  = -(SYSCLK / 12 / BLINK_RATE);  // Init reload values
   TMR3    = 0xffff;                   // Set to reload immediately
   EIE1    |= 0x80;                    // Enable Timer3 interrupts
   TMR3CN  |= 0x04;                    // Start Timer3
}

//------------------------------------------------------------------------------------
// Interrupt Service Routines
//------------------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// TIMER3_ISR
//-----------------------------------------------------------------------------
//
// This ISR is triggered upon a Timer3 overflow.  The ISR simply toggles
// the state of the LED and keeps track of the number of times the LED blinks.
//
//-----------------------------------------------------------------------------
void
Timer3_ISR(void) interrupt 14
{
   TMR3CN &= ~0x80;                    // Clear Timer3 Flags
   LED = !LED;
   Num_LED_Flashes++;
}