Introduction of SCM IO port configuration mode

1. Quasi-bidirectional port

2, two-way port

The difference between the two-way port and the quasi-bidirectional port is mainly: the quasi-bidirectional port I/O port operation when the data input needs to be set 1, otherwise if the previous bit is low, the latter input level is high then the MOS tube can not pull up resulting in an error. The two-way port does not require this action, because the two-way Port has a suspended state.

Quasi-bidirectional port is to do the input when you have to write to the latch 1 of this preparation action, so called quasi-bidirectional port.

A true bidirectional port does not require any pre-operation to read directly into the read-out.

1> quasi-bidirectional generally can only be used for digital input and output, the input is a weak pull-up state (about 50K pull up), the port has only two states: High or low.

The 2> bidirectional is used for analog input and output in addition to digital input and output, and the port is set to a high impedance input state via direction control when analog input. Two-way ports have three states: high, low, or high resistance.

3> the initial state and the reset state of the quasi-bidirectional port is 1, the bidirectional port is a high-impedance state. There is a microcontroller with some comparator, the input of the comparator can only be done in the bidirectional port, can not do in the quasi-bidirectional port. So the first step in software design is to set the I/O port.

3. Open-Drain

The open-drain mode is similar to the quasi-bidirectional mode, but does not have an internal pull-up resistor. The advantage of open-drain mode is good electrical compatibility, external pull-up resistor 3V power supply, you can and 3V logic device interface, if the pull-up resistor 5V power supply, but also with the 5V logic device interface. In addition, the open-drain mode makes it easy to implement "line and" logic functions.

4. Push-Pull output

The push-pull output is characterized by the ability to drive large currents regardless of the output high or low level

Introduction of SCM IO port configuration mode