A small feedback circuit, typically consisting of two weak cross-coupled inverters, placed on a tri-state bus line. When all connected devices go into a high-impedance state, the bus-holder gently holds the line at its last driven voltage level (high or low). This prevents the bus from floating to an intermediate voltage, which would waste power and cause unpredictable switching in connected logic gates.
We need a bus-holder on the data lines so the inputs don't float and cause shoot-through current during the idle cycles.
Bus-holders eliminate the need for external pull-up or pull-down resistors on data buses, saving board space and reducing static power consumption.
Also heard as
- bus keeper
Related terms
Logic level
A specific voltage range that represents a distinct binary state in a digital circuit.
Pull-up resistor
A resistor connected between a logic pin and a positive supply voltage to hold the line at a logic high state.
Pull-down resistor
A resistor connected between a logic pin and ground to hold the line at a logic low state.