Running Models built with R2008b in R2013b

I am an electronics engineer and I had been working with Matlab 2008b for a long time. Recently I updated the version to 2013b and now I started having this problem. The problem I am having is as follows, I had built customized simulink models in r2008b for the purpose of data acquisition. I had used Real Time Windows Target tool box to acquire and generate signals from National Instruments DAQ cards. As soon as I had upgraded to r2013b my models run no more. When I dig down a little bit I found that the "Analog Input" and "Analog Output" block of Real Time Windows Target have been modified due to which the models are not running properly. Why this has been done? In all other languages the newer versions support the codes written in previous versions but why this is not available in Matlab? I wish to know the workaround if there exists any? Hoping for a prompt response. Ehtisham Safdar