arduino - Arduino/Attiny85：ISR 和端口操作延迟

Question

我试图让一个引脚上的输出与另一个播放 a 的输出相关tone()，但有 35us @8MHz 或 158us @1MHz 时钟的延迟。似乎有一个固定的 16us +142 个时钟周期延迟，因为延迟与时钟频率不成反比。它们非常非常长！为什么？

这是代码：

/* Per ATTINY85:
1: I/O5 PB5 A0 RS 
2: I/O3 PB3 A3          - Geiger inverted earphone out
3: I/O4 PB4 A2          - Geiger earphone out
4: GND
5: I/O0 PB0    MOSI SDA - Battery test/Geiger LED out
6: I/O1 PB1    MISO     
7: I/O2 PB2 A1 SCLK SCL INT0 - Geiger probe in (via NPN transistor)
8: Vcc
*/

#include<avr/sleep.h>

byte state;
volatile byte P;
int B;
int Bo;
byte LED=0;
unsigned long t=0;

void particella() 
{
    P=1;
}

ISR(PCINT0_vect)
{
    if (!(PINB & (1<<PB4)))
        PORTB |= (1<<PB3);
    else 
        PORTB &= ~(1<<PB3);
}

void setup()
{
    pinMode(0, OUTPUT); // Al LED.
    pinMode(2, INPUT); // Dal transistor dal tubo Geiger.
    pinMode(2, INPUT_PULLUP); // Pull-up per il collettore del transistor.
    pinMode(4, OUTPUT); // All'auricolare.
    pinMode(3, OUTPUT); // All'auricolare (copia invertita del 4).

    GIMSK = 0x60;    // turns on external and pin change interrupts.
    PCMSK = 0x10;    // turn on interrupts on pin PB4.
    sei();           // set interrupts (enable).

    tone(4,2000,100); // Power on beep
    PORTB|=0b00000001;
    delay(700);
    PORTB&=0b11111110;
    delay(1000);
    readVcc();

    for(byte n=1; n<=state; n++)
    {
        PORTB|=0b00000001; // Accende il LED su I/O0 = PB0
        tone(4,2000,25); // Bip acuto a ogni lampo.
        delay(30);
        PORTB&=0b11111110; //  Spegne il LED su I/O0 = PB0
        delay(250);
    }
    delay(350);

    attachInterrupt(0, particella, FALLING);
}


void loop()
{
    if(P)
    {
        P=0;
        t=millis();
        PORTB|=0b00000001; // Accende il LED su I/O0 = PB0
        LED=1;
        tone(4,1000,5); // Fa TIC nell'auricolare.
    }

    if(millis()-t>=10 && LED==1) 
    {
        LED=0; PORTB&=0b11111110; //  I/O0 = PB0 LED OFF after 10ms.
    }
}