[51] How do detect duration of external input state

[hithesh123]

How do I find out how long an input pin has changed logic state.
Let me explain -

In some buses, the host pulls down the clock or data line for a particular duration to request access.
How can I detect this in a MCU like 8051.
The MCU is C8051F120. The two interrupts (INT0 and INT1) have already been used.

 

[Gorgon]

You could make the interrupt system more intelligent, if you combine a set og flipflops with a register and use one of the INT inputs to a sum of all interrupt flipflops, you need som more intelligence in the ISR to separate the active interrupt and process this part of the ISR.
You normally use the timer/ counter to calculate elapsed time.

The ideal way to this is to change to a more modern microcontroller, with these functions inbuilt.