Power saving method is achieved by weakly holding a signal line in its last in time state, which is responsive to and may be overcome by the state of an external signal. During sleep mode, the weakly held signal line state tracks and holds the external signal using alternatively a controllable weak pull-up or pull-down device, such that weakly held state may be driven to a different state by the external driving signal with slight power consumption. When sleep mode is off, the keeper function is disabled and the signal line maybe driven alternatively internally or externally depending upon the state of an enable line.