Tool/software:
I am debugging the circuit related to 555 timer, and I have a question to consult you.
1. Usage
Under normal circuit conditions, the voltage of THRESHOD is < 2/3Vcc, and its voltage remains constant. The TRIG voltage switches between 0V and Vcc, and the TRIG level remains high for a long time. When the 555 timer is used every 150us, when in use: the MCU connects the TRIG pin and sends a negative pulse signal (pulse time 5us) to it, which will cause: OUTOUT output high level, and maintain high level. The OUTPUT signal is then used elsewhere.
When there is interference in the circuit, the voltage of THRESHOD is > 2/3Vcc, and the single-chip microcomputer controls the TRIG pin to send the negative pulse signal, and the OUTPUT will output a positive pulse signal and then keep the low level. By detecting this low level to determine whether the circuit is abnormal.
The cycle is 150us, each cycle to perform 16 cycles, interference signals will only affect 1 cycle.
For example, when the fifth period is interfered with, the OUTPUT signal of the fifth period is abnormal and the abnormal situation of the fifth period is processed accordingly. Number six, seven, eight... The detected OUTPUT signal is normal and will not be processed.
2. Question consultation
The program has to do a lot of other work in the 150us cycle, so the pulse time can not be too long. At first, the duration of the negative pulse signal I sent was 1us, but it will lead to the interference in the 5th cycle, and all the following signals are abnormal, 2us, 3us, 4us, and so on.
After 5us, 6us and 10us, it can work normally, and the period with interference can be detected, without affecting the period without interference.
What I want to ask is: What is the minimum negative pulse time?
