The ex Keypad includes 16 hex buttons, an IN button and 2 LEDs:
In load mode (see Front Panel) specify a hex value by clicking two hex buttons (yellow ellipse). After this click the IN button (orange ellipse) and the specified value will be written into the memory location in R[0]. When the left LED (magenta ellipse) is on the first nibble can be specified and when the right LED (blue ellipse) is on the second nibble can be specified.