Executing different operqtiions from same simulink file

I am working on two different S-Functions connecting two different devices,in the same simulink model. Each S-Funnction works perfectly well independently on its own simulink model

The problem is, when I combine the two models into one and run the combined model, I cannot get the readings from my second device continously,but rather, it waits for the first device to finish its cylce of operation and the it gives an output, also,sometimes the port of the device changes. I would like to get the readings independently from the combined model. Kindly help.