Dataman 48UXP - Manual (Page 40)

devices, the option is used to modify the vectors that will be
used to test a device after the logical chip has been program,
this test vector is usually generated by other PLD design tool
when the circuit diagram and layout for chip is done. The
JEDEC file is downloaded into the Dataman-48UXP, and it
also contains the test vector that will be used to test the device
for correct programming and function. The follow screen will
be displayed when enable the Modify Vector:
The purpose of the buttons are as following:
Undo
When the changes are made, the changed areas are
highlighted. If you wish to undo this change, just can click
this button. It will restore the value prior to the editing
done. When a position that is highlight scrolls off the
screen, the changed made become permanent and you
cannot reverse these changes by clicking this button.