TMS320F28335: Embedded coder ADC module B problem

I am using TMS320F28335 DSP and Matlab R2018a. I have written the code in matlab simulink for changing PWM using ADC input voltage from Potentiometer connected to one of ADCIN pin. So when I select the DSP Module in the ADC block as B and input pin between ADCINB0-B7 it doesn’t vary the PWM signal by varying voltage from Pot But when I select the DSP Module in the ADC block as A and input pin between ADCINA0-A7 then it does vary the PWM signal by varying voltage from Pot. Also if I select Module as A and B and input pin as ADCINB0-B7 then also vary the PWM signal by varying voltage from Pot. Why only selecting the DSP Module in the ADC block as B and input pin between ADCINB0-B7 has problem?