TMS320F2812: I use tms320f2812 ,have some problems about the ADC

Hi all:

    when  I use tms320f2812 inside ADC, the Voltage signal into the ADC pin is smoothly, In order to observe the voltage signal I use TLC5615( a DAC) .They  I Connect these signals  to the oscilloscope. I found the signal from DAC not smoothly,some points are high,some points low, the wave as blow, red is the voltage signal into the ADC ,blue and yellow  are the signal form DAC.  Is there a problem with my test method?Thanks a lot.