Both the input and output of the MSP430 can be set with pull-up and pull-down resistors. Whether the pull-up is determined by the REN register, but whether it is pulled up or pulled down is determined by the OUT register. When it is output, it automatically selects up and down with the level of OUT; when it is input, it can be artificially Assign the OUT register to get the up and down. 1. When the TTL circuit drives the COMS circuit, if the high level of the TTL circuit output is lower than the lowest level of the COMS circuit (generally 3.5V), then the pull-up resistor needs to be connected at the output end of the TTL to improve Output a high value. 2. The OC gate circuit must be equipped with a pull-up resistor to increase the level of the output. 3, in order to increase the drive capability of the output pin, some of the microcontroller pins often use pull-up resistors. 4. On the COMS chip, in order to prevent damage caused by static electricity, the unused pins cannot be suspended. Generally, the pull-up resistor is connected to reduce the input impedance and provide a discharge path. 5. The pin of the chip is added with a pull-up resistor to increase the output level, thereby improving the noise margin of the input signal of the chip and enhancing the anti-interference ability. 6. Improve the anti-electromagnetic interference capability of the bus. When the pins are suspended, it is easier to accept external electromagnetic interference. 7. The resistance mismatch in long-line transmission is easy to cause reflected wave interference, and the pull-down resistor is resistance matching, which effectively suppresses reflected wave interference. 1. It should be large enough to save power and the current sinking capacity of the chip; the resistance is large and the current is small. 3. For high-speed circuits, excessive pull-up resistors may flatten the edges. Consider the above three points, usually between 1k and 10k. voidInit_keypad_Port(void) { P1SEL&=~KEY_MOD;//Set the keyboard port to I/O port P1DIR|=KEY_MOD;P1REN|=KEY_MOD+BIT7; P1OUT|=KEY_MOD; P1OUT&=~BIT7;//Set mode select port as pull-down resistor P1REN&=~(KEY_MOD+BIT7); P1DIR&=~(KEY_MOD+BIT7);//Set the line port as the input port P1IFG=0; P1IES&=~BIT7;//Set manual mode port rising edge interrupt P1IE|=BIT7;//Manual mode select port interrupt enable } PxREN is the enable register for setting pull-up or pull-down. When enabled, it is enabled. When enabled, pull-up or pull-down is set by PxOUT. Explosion-proof Screen Protector The Explosion-proof Screen Protective Film for mobile phones is a protective film that can effectively buffer the impact, prevent the screen from bursting, or prevent the glass panel from being broken and scattered due to accidental impact of the mobile phone. Screen protector with gloss, texture and surface hardness. PET Screen Protector, Explosion-proof Screen Protector, Explosion-proof Screen Protective Film, Explosion-proof Protective Film Shenzhen Jianjiantong Technology Co., Ltd. , https://www.tpuprotector.com
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Msp430 introduces the use of _msp430 pull-up resistor
2. It should be small enough to ensure sufficient driving current; the resistance is small and the current is large.