A pressure medium-operated percussion device of a rock breaking device arranged to provide impact pulses to a rock breaking tool, the percussion device comprising: a frame; a percussion piston that is during its work cycle arranged to move axially back and forth in an impact direction and a return direction, when a pressure medium acts on its working pressure surfaces (34a, 34b); at least one pressure-controlled mechanical control valve (40, 77) having positions for directing the pressure medium to act on at least one working pressure surface of the percussion piston and away from it for the purpose of controlling the work cycle of the percussion piston, the control valve being equipped with pressure surfaces and the control valve being arranged to move between its extreme positions under the influence of the pressure medium acting on the surfaces; at least one impulse space (44, 45), which is an annular space around the percussion piston; at least one surface (K1, K2) on the percussion piston which defines the impulse space (44, 45) in the axial direction and reduces the volume of the impulse space as the percussion piston moves toward it; the impulse space (44, 45) having at least one first pressure connection (58, 59) to at least one pressure surface of the control valve; and the impulse space (44, 45) having at least one second pressure connection (Y1, Y2); at least one impulse edge (S1, S2) on the percussion piston for closing the second pressure connection (Y1, Y2), whereby the impulse space becomes a closed pressure space and a pressure pulse is generated; the pressure pulse acting on the control valve (40, 77) through the first pressure connection and providing its alternating movement an initial impulse toward its opposite extreme position; wherein, when seen in a radial direction of the percussion piston, the impulse space (44, 45) is defined by the percussion piston and the frame; and the first pressure connection comprises at least one impulse channel (58, 59) provided in the frame; and wherein the control valve is provided with a holding circuit being arranged to direct pressure medium to the control pressure surfaces of the control valve and to hold the control valve in place in its extreme positions until the pressure pulse directed from the at least one impulse space causes a momentary force effect to the control valve and moves the control valve towards the opposite end position; and the forces generated by the holding circuit are configured to complete the movement of the control valve to the opposite end position, where the control valve remains waiting for the next pressure pulse and the subsequent movement to the opposite end position. a frame; a percussion piston that is during its work cycle arranged to move axially back and forth in an impact direction and a return direction, when a pressure medium acts on its working pressure surfaces (34a, 34b); at least one pressure-controlled mechanical control valve (40, 77) having positions for directing the pressure medium to act on at least one working pressure surface of the percussion piston and away from it for the purpose of controlling the work cycle of the percussion piston, the control valve being equipped with pressure surfaces and the control valve being arranged to move between its extreme positions under the influence of the pressure medium acting on the surfaces; at least one impulse space (44, 45), which is an annular space around the percussion piston; at least one surface (K1, K2) on the percussion piston which defines the impulse space (44, 45) in the axial direction and reduces the volume of the impulse space as the percussion piston moves toward it; the impulse space (44, 45) having at least one first pressure connection (58, 59) to at least one pressure surface of the control valve; and the impulse space (44, 45) having at least one second pressure connection (Y1, Y2); at least one impulse edge (S1, S2) on the percussion piston for closing the second pressure connection (Y1, Y2), whereby the impulse space becomes a closed pressure space and a pressure pulse is generated; the pressure pulse acting on the control valve (40, 77) through the first pressure connection and providing its alternating movement an initial impulse toward its opposite extreme position; wherein, when seen in a radial direction of the percussion piston, the impulse space (44, 45) is defined by the percussion piston and the frame; and the first pressure connection comprises at least one impulse channel (58, 59) provided in the frame; and wherein the control valve is provided with a holding circuit being arranged to direct pressure medium to the control pressure surfaces of the control valve and to hold the control valve in place in its extreme positions until the pressure pulse directed from the at least one impulse space causes a momentary force effect to the control valve and moves the control valve towards the opposite end position; and the forces generated by the holding circuit are configured to complete the movement of the control valve to the opposite end position, where the control valve remains waiting for the next pressure pulse and the subsequent movement to the opposite end position.