Circuit structure and output mode of GPIO port of 32-bit single chip microcomputer

Or take Huada 32 Bit MCU to explain , In fact, everyone is generally the same structure

Above device analysis ：

1、 Protection diode ： prevent I/O Pin outside too high 、 Low voltage input , Prevent abnormal voltage from being introduced into the chip and causing the chip to burn . See the previous article for details

2、 switch ： The switch is TTL Schottky trigger , Convert an analog signal to 0 and 1 The digital signal of , But when GPIO As ADC When collecting voltage channel , At this time, the signal does not go through the trigger TTL Level conversion .

3、P-MOS、N-MOS： The unit circuit makes GPIO have “ Push pull output ” and “ Open drain output ” The function of
 

4 Input mode

32 With floating input 、 Pull up input 、 Pull down inputs and analog inputs 4 Input mode .

Floating input mode ,I/O The level signal of the port is determined by the external input , The level state is uncertain , Floating input is usually used to configure USART Of RX Pin , As shown in the figure below ：

Pull up input mode ,I/O The port level state remains high , When the input power is low , The level state changes to low level , Finally enter the input data register , As shown in the figure below ：

Drop down input mode ,I The level state remains low , When the input power is high , The level status changes from white to high , Finally enter the input data register , As shown in the figure below ：

Analog input mode ,I/O Analog signal of the port （ Voltage signal , Not the level signal ） Direct analog input to on-chip peripheral modules , such as ADC Module etc. . Analog inputs are usually used for ADC Analog input , Or low power consumption, power saving, etc , As shown in the figure below ：

 

 

4 Output mode

Open drain output mode , Set by configuration / Reset register or output data register value , control N-MOS tube , Output to I/O port . Open drain output can only output strong low level , The high level depends on the external resistance ,

Push pull output mode , Set by configuration / Reset register or output data register value , control P-MOS Tube and N-MOS tube , Output to I/O port . Push pull output can be strong 、 Low level , As shown in the figure below ： 

 

  Multiplexing function open drain output mode 、 The principle of push-pull output mode and open drain output mode of multiplexing function 、 Push pull output mode principle is basically the same , It's just decided by using the multiplexing function output of on-chip peripheral modules （ communication interface （SPI,UART,I 2 C,USB,CAN,LCD etc. ）、 Timer 、 Reuse of debugging interface, etc ）. Multiplexing function open drain output is usually used for TX1、MOSI、MISO Wait for pin configuration , Push pull output of multiplexing function is usually used for I2C Of SCL、SDA.

Be careful ： Know everything GPIO After function , For application scenarios, we should learn to judge when to use what mode , It's worth noting that , For low-power scenarios , We can put IO Configured as analog input , Avoid current leakage