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This device is for protection purpose.
Each time you connect the emulator to a board, is better you safe too much the emulator because the board (tipically a prototype) can have trouble, and damage the emulator.
So in case of damage, is better you damage a line driver instead of CPLD.
Removing line driver reduce a few the size of emulator, but unprotect it from external faults.
This chip is a TAP ..there is at opencores.org a TAP core that coud be used as a "starting point" but the 74ACT8990 has more functionnality that need to be inluded .. It only makes sense if you want to replace several chips and the 74ACT8990 included .Otherwise Bobcat is right .It's not worthy it can be ordered from digikey .