xPC Target model execution using external trigger

I searched up the matlab answers and found one related question. Solution provided was of using parallel port, IRQ 7, 0x378 and give a rising edge on pin 10 ACK of parallel port. When I load and start the model on xPC Target, it shows status 'running' and when I give a 5 volt signal on pin 10 of parallel port and use ground as well, it changes to time 0.0s and does not advance. After a while I stop the execution and the xPC target shows:

System: execution stopped at 0.00000. System: minimal TET: 9999999.000000 at time 0.000000. System: maximal TET: 0,000000 at time 0.000000. System: average TET: -1.#IND00.

Is there anything wrong I am doing with the signal?