MATLAB: How to use negative transition of CTR05 interrupt source to start the simulation in xPC Target 4.1 (R2009a)

Simulink Real-Time

I am using CTR05 as an interrupt source. I want to start my simulation on the negative transition of the interrupt signal as I am syncing xPC target with another device which uses the downward transition.

Best Answer

The CTR05 driver block is setup to use upward transitions. Changing the interrupt polarity to low, forces CRT05 to be level-triggered rather than edge triggered.
Thus, CTR05 cannot be made to work with low polarity while still being edge triggered.
Inverting the signal external to xPC Target is the only workaround.