The purpose of the pump is only to generate the pressure that would otherwise come from the brake pedal. The ABS, if it is active because a wheel indicates zero rotation, separates the pressure from the pedal on the brake pistons and the pressure from the pump takes over this task. About the four valves in the ABS block is then controlled on which brake disc pressure is exerted or not. Another mode of operation of the pump does not exist to my knowledge.
