F28069 Simulink Time Step

Hi all,

I'm trying to produce a simple simulink model to read data from four SPI slave ADCs. The f28069m SPI peripheral has only on "Chip Select" line so I have taken TI's advice and used GPIO pins as "Chip Select" lines.

When I run this on the external target, it executes MUCH slower than I would expect. The time step for the program would appear to be 100ms, as shown in the attached oscilloscope capture. How can a change this time step as it is set to 100e-6 in the simulation settings?

Thanks.