DE2 Link_D0 to LINK_D3 for what purpose?

Hi there,

I am not quite understanding what's the purpose for Link_D0 to LINK_D3 on DE2 board.

Enclosed is the schematic file.

On page 21, to my understanding,

• Pin 64 (TDO), Pin 63 (TCK), Pin 61 (TMS) and Pin 60 (TDI) of U26 (EPM3128) are for JTAG programming

• Pin 54 - Pin 57 of U26 are for AS programming

• Pin 28 (TRGOE) is for choosing AS or JTAG programming through SW19

I don't know what's the purpose for Pin 69 - Pin 72 of U26 or LINK_D0 to LINK_D3.

Anybody can help?

Thanks a lot!