Interrupts

The CH552 microcontroller supports 14 sets of interrupt signal sources. These include 6 sets of interrupts (INT0, T0, INT1, T1, UART0, and T2), which are compatible with the standard MCS51, and 8 sets of extended interrupts (SPI0, TKEY, USB, ADC, UART1, PWMX, GPIO, and WDOG). The GPIO interrupt can be chosen from 7 I/O pins.

Table 4 Default priority sequence of interrupt sources

Interrupt src.	Entry addr.	Interrupt #	Description	Default prio. seq.
INT_NO_INT0	0x0003	0	External interrupt 0	High priority
INT_NO_TMR0	0x000B	1	Timer 0 interrupt	↓
INT_NO_INT1	0x0013	2	External interrupt 1	↓
INT_NO_TMR1	0x001B	3	Timer 1 interrupt	↓
INT_NO_UART0	0x0023	4	UART0 interrupt	↓
INT_NO_TMR2	0x002B	5	Timer 2 interrupt	↓
INT_NO_SPI0	0x0033	6	SPI0 interrupt	↓
INT_NO_TKEY	0x003B	7	Touch key timer interrupt	↓
INT_NO_USB	0x0043	8	USB interrupt	↓
INT_NO_ADC	0x004B	9	ADC interrupt	↓
INT_NO_UART1	0x0053	10	UART1 interrupt	↓
INT_NO_PWMX	0x005B	11	PWM1/PWM2 interrupt	↓
INT_NO_GPIO	0x0063	12	GPIO Interrupt	↓
INT_NO_WDOG	0x006B	13	Watchdog timer interrupt	Low priority

The interrupt priority is determined by the interrupt number.

Timer 0/1 Interrupts

Timer0 and Timer1 are 16-bit timers/counters controlled by TCON and TMOD. TCON is responsible for timer/counter T0 and T1 startup control, overflow interrupt, and external interrupt control. Each timer consists of dual 8-bit registers forming a 16-bit timing unit. Timer 0’s high byte counter is TH0, and its low byte counter is TL0. Similarly, Timer 1’s high byte counter is TH1, and its low byte counter is TL1. Timer 1 can also serve as the baud rate generator for UART0. code example:

void timer0_interrupt(void) __interrupt(INT_NO_TMR0)        /* Timer0 interrupt service routine (ISR) */
{
    PIN_toggle(PIN_BUZZER);
    TH0 = 0xFF;             /* 50ms timer value */
    TL0 = 0x00;
}


int main(void)
{
    CLK_config();
    DLY_ms(5);
    PIN_output(PIN_BUZZER);
    EA  = 1;                /* Enable global interrupt */
    ET0 = 1;                /* Enable timer0 interrupt */

    TH0 = 0xFF;             /* 50ms timer value */
    TL0 = 0x00;
    TMOD = 0x01;            /* Timer0 mode1 */
    TR0 = 1;                /* Start timer0 */
    while(1);
}

External Interrupts

INT0 and INT1 are external interrupt input pins. When an external interrupt occurs, the corresponding interrupt service routine is executed. The external interrupt can be triggered by the falling edge, rising edge, or both edges of the external interrupt input signal. The trigger mode is determined by the external interrupt input pin.

code example:

void ext0_interrupt(void) __interrupt(INT_NO_INT0)
{
    PIN_toggle(PIN_LED);
}

int main(void)
{
    CLK_config();
    DLY_ms(5);
    PIN_output_OD(PIN_INT);
    PIN_output(PIN_LED);

    EA  = 1;     /* Enable global interrupt */
    EX0 = 1;    // Enable INT0
    IT0 = 1;    // INT0 is edge triggered

    while(1)
    {
        // Do nothing
    }

}