1、Chip STC12C5204AD I/O port configuration STC12C5204AD series microcontroller its all I/O ports are controlled by the software configuration into 4 kinds of work type 4 types are respectively: quasi two-way mouth (standard the 8051 output mode), push-pull output, only for input (high resistance) or o
2、pen-drain output functions. Every mouth consists of two control register the relevant position control each pin type of work. STC12C5204AD series microcontroller to electricity reattachment shall prevail two-way mouth (standard the 8051 output mode) mode: 2V above high level, 0.8 V for low level bel
3、ow. 1. Quasi two-way mouth output configuration Quasi two-way mouth output type can be used as output and input function but dont need to reconfigure mouth lines output state. This is because juncture lines output is 1 drive ability is very weak, allowing external devices will its down. When pins fo
4、r low, it output driving ability, can absorb the considerable current. Quasi two-way mouth have 3 pull_up transistor adapted to different needs. In the three and one transistor, pull up transistor called weak on pull , for 1 and paternal line registers itself pins for 1 open. This pull_up provides b
5、asic drive current make prospective two-way mouth for 1 output. If a pin for 1 and output by external devices to drop down to low, pull up close and weak very weak pull_up maintain open position, in order to put this pin for low, strong to pull the external devices must have enough power to make pin
6、 infused current threshold voltage of a voltage to the following. Article 2 pull_up transistors, called extremely weak on pull, 1 latch paternal line when open. When pin, the very weak suspended the pull_up source generates very weak and current will pin and high level. Article 3 pull_up transistor
7、called powerful pull. Juncture line latches from 0 to 1, the jumping to accelerate must pull up by logic 0 to two-way mouth logic 1 conversion. When this happened, powerful pull open about 2 machine cycle to make pins can quickly pull to the earth high level. Quasi two-way mouth output shown below.
8、STC12C520 series microcontroller 3V device, if the user is in pins plus 5V voltage, there will be a current flow from pins, this has caused additional VDD power consumption. Accordingly, the proposal is not in quasi two-way mouth mode 3V microcontroller pins to exert 5V voltage, such as the use of w
9、ords, will add current limiting resistor, or using diode do input isolation, or use triode do output segregation. Quasi two-way mouth with a schmidt trigger input and a interference suppression circuit. 2. The push-pull output configuration The drop-down push-pull output configuration open-drain out
10、put and the structure and the prospective two-way mouth down same structure, but when latches is 1 provides continuous strong pull up. The push-pull model need more commonly used for driving current situation. The push-pull pins configuration are shown below. 3. Only for input (high resistance) conf
11、iguration Input port configuration are shown below. Input port with a schmidt trigger input and a interference suppression circuit. 4. Open-drain output configuration Juncture line latches is 0, the open-drain output close all pull_up transistors. When, as a logical output, this configuration mode m
12、ust have externally pull, usually by resistance receiving V D D outside. This style of drop-down and quasi two-way mouth the same. The jammer line configuration are shown below. Open-drain port with a schmidt trigger input and a interference suppression circuit. A typical transistor control circuit
