@Costas
Thank you very much for your advice.
Sorry for asking again but I do not understand the reference @ https://www.arduino.cc/en/Reference/detachInterrupt
Could you please advice me how to use "detachInterrupt " for the example below ?
noInterrupts();
timer0_isr_init();
timer0_attachInterrupt(timer0_ISR);
timer0_write(ESP.getCycleCount() + 80000000L); // 80MHz == 1sec
interrupts();