Implantable pacemaker is a battery operated real time embedded system, which includes software/hardware co-design strategy. As it is placed within the heart by surgery, battery life is an important constraint to extend device lifetime. In this paper, pacemaker's functionalities like basic pacing, pulse width, refractory period in VOO mode has been realized using ultralow power processor MSP 430F1611 and IAR workbench. Software related instruction level instantaneous current is measured and Current/Energy performance, battery longevity is tested. It is verified that, change in pure cost and inter-instruction cost (current/energy) varies from 2.0 to 3.0%.