Analysis on the pull-up resistor in the digital tube circuit of the single-chip microcomputer

The pull-up is to clamp the uncertain signal to a high level through a resistor, and the resistor also acts as a current limiter. The pull-down is the same, and the uncertain signal is clamped to a low level through a resistor.

The pull-up is the input current to the device, and the pull-down is the output current; the strength is only the difference in the resistance of the pull-up resistor, and there is no strict distinction; it provides current for non-collector (or drain) open-circuit output circuits (such as ordinary gate circuits) The ability to sum the voltage is limited. The function of the pull-up resistor is mainly to output the current channel for the open-collector output circuit.

Digital tube is also called LED digital tube, according to the connection mode of light-emitting diode unit can be divided into common anode digital tube and common cathode digital tube. The common anode digital tube refers to the digital tube that connects the anodes of all light-emitting diodes to form a common anode (COM). The common anode digital tube should be connected to +5V when the common anode is used. When the cathode of a certain field of light-emitting diodes When it is low level, the corresponding field is lit, and when the cathode of a field is high, the corresponding field is not lit.

Common cathode digital tube refers to the digital tube that connects the cathodes of all light-emitting diodes to form a common cathode (COM). The common cathode digital tube should be connected to the ground line GND when the common cathode digital tube is used. When a certain field of light-emitting diodes When the anode of a field is high, the corresponding field is lit, and when the anode of a field is low, the corresponding field is not lit.