CCS/DS90UB901Q-Q1: DS90UB901 and DS90UB902 GPIO is not connect

Tool/software: Code Composer Studio

Hi

I used DS90UB901 and DS90UB902 to Transfer video data。

I config DS90UB901 and DS90UB902 as salve mode, The local HOST to config the device register 

The video data transmission is OK, then the GPIO pins is blocked！！！

I set The 902 register to configure the GPIO[1:0] as input pin as follow
registerID Value
0x1D        0x17
0x1E        0x07

I set the 901 register to configure the GPIO[1:0] as ouput pin as follow
registerID Value
0x0D         0x11
0x0E         0x01

Then I pull up the 902 GPIO[1:0] pins by configure TDA3x pins which connect to 902 GPIO[1:0] pins,
waiting a moment then push down the 902 GPIO[1:0] to generate the wave .

But I can not capture the wave in DS901 GPIO[1:0]

What‘s reason cause it??????