//-----------------------------------------------------------------------------
// Global Constants
//-----------------------------------------------------------------------------
#define SYSCLK 24500000/8 // SYSCLK in Hz (24.5 MHz internal
// oscillator / 8)
// the internal oscillator has a
// tolerance of +/- 2%
#define TIMER_PRESCALER 48 // Based on Timer CKCON settings
#define LED_TOGGLE_RATE 50 // LED toggle rate in milliseconds
// if LED_TOGGLE_RATE = 1, the LED will
// be on for 1 millisecond and off for
// 1 millisecond
// There are SYSCLK/TIMER_PRESCALER timer ticks per second, so
// SYSCLK/TIMER_PRESCALER/1000 timer ticks per millisecond.
#define TIMER_TICKS_PER_MS SYSCLK/TIMER_PRESCALER/1000
// Note: LED_TOGGLE_RATE*TIMER_TICKS_PER_MS should not exceed 65535 (0xFFFF)
// for the 16-bit timer
#define AUX1 TIMER_TICKS_PER_MS*LED_TOGGLE_RATE
#define AUX2 -AUX1
#define AUX3 AUX2&0x00FF
#define AUX4 ((AUX2&0xFF00)>>8)
#define TIMER0_RELOAD_HIGH AUX4 // Reload value for Timer0 high byte
#define TIMER0_RELOAD_LOW AUX3 // Reload value for Timer0 low byte
sbit LED = P1^3; // LED='1' means ON
//-----------------------------------------------------------------------------
// Function Prototypes
//-----------------------------------------------------------------------------
void Port_Init (void); // Port initialization routine
void Timer0_Init (void); // Timer0 initialization routine
//-----------------------------------------------------------------------------
// main() Routine
//-----------------------------------------------------------------------------
void main (void)
{
PCA0MD &= ~0x40; // Clear watchdog timer enable
Timer0_Init (); // Initialize the Timer0
Port_Init (); // Init Ports
EA = 1; // Enable global interrupts
while (1); // Loop forever
}
//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Port_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This function configures the crossbar and GPIO ports.
//
// Pinout:
//
// P1.3 -> LED
//
// all other port pins unused
//
//--------------------------------
---------------------------------------------
void Port_Init (void)
{
XBR1 = 0x40; // Enable crossbar
P1MDOUT = 0x08; // Set LED to push-pull
}
//-----------------------------------------------------------------------------
// Timer0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This function configures the Timer0 as a 16-bit timer, interrupt enabled.
// Using the internal osc. at 12MHz with a prescaler of 1:8 and reloading the
// T0 registers with TIMER0_RELOAD_HIGH/LOW it will interrupt and then toggle
// the LED.
//
// Note: The Timer0 uses a 1:48 prescaler. If this setting changes, the
// TIMER_PRESCALER constant must also be changed.
//-----------------------------------------------------------------------------
void Timer0_Init(void)
{
TH0 = TIMER0_RELOAD_HIGH; // Init Timer0 High register
TL0 = TIMER0_RELOAD_LOW ; // Init Timer0 Low register
TMOD = 0x01; // Timer0 in 16-bit mode
CKCON = 0x02; // Timer0 uses a 1:48 prescaler
ET0 = 1; // Timer0 interrupt enabled
TCON = 0x10; // Timer0 ON
}
//-----------------------------------------------------------------------------
// Interrupt Service Routines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Timer0_ISR
//-----------------------------------------------------------------------------
//
// Here we process the Timer0 interrupt and toggle the LED
//
//-----------------------------------------------------------------------------
void Timer0_ISR (void) interrupt 1
{
LED = ~LED; // Toggle the LED
TH0 = TIMER0_RELOAD_HIGH; // Reinit Timer0 High register
TL0 = TIMER0_RELOAD_LOW; // Reinit Timer0 Low register
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