Simulink: Serial Receive Block too slow ?

I am currently working with the Serial Receive Block to transfer data from a microcontroller to Simulink.

I set the baudrate to 115200 and the controller sends 1 databyte every 100 µs. The model stops when 4000 databytes are received. Unfortunately this process takes more than 1 minute !

I expect the transfer to be finished after 4000 x 100 µs = 400 ms.

What could be the problem ? The baudrate should be correct, because the data I receive is valid.

Thank you in advance.