How can I use Pin55 of TMS570LS0714PGE as an output pin

Hi,

I noticed that the chip(TMS570LS0714PGE)has 2 output ports named GIOB2, pin142 and pin55.

And pin55 has functions as follows,

but in HCG ,pin55' configuration item is grey and can not be configured as any function other than GIOB2.

And it doesn't output anything.

Can you tell me how I can use pin55 as an output pin?

thank you .