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Which of the following port requires external pull-up resistor?
Features of Port 0 An external pull-up resistor is needed when Port 0 is defined as an output port. Port 0 of the 8051 has two main functions: To be used as a simple input-output port and to access external memory in conjunction with Port 2.
Which port do not require any pull up resistor?
Input/Output (I/O) pin − All the circuits within the microcontroller must be connected to one of its pins except P0 port because it does not have pull-up resistors built-in. Input pin − Logic 1 is applied to a bit of the P register.
How many pull up resistor are used in port 0?
Full Member level 5. Pull-ups are used so that components with a different driving voltage can be connected to the microcontroller.
What do you need to know about pull up resistors?
The short and easy answer is that you want a resistor value on the order of 10kΩ for the pull-up. A low resistor value is called a strong pull-up (more current flows), a high resistor value is called a weak pull-up (less current flows). The value of the pull-up resistor needs to be chosen to satisfy two conditions:
How big of a pull up resistor do I need for TTL?
A standard TTL input at logic “1” is normally operated assuming a source current of 40 µA, and a voltage level above 2.4 V, allowing a pull-up resistor of no more than 50 kohms; whereas the TTL input at logic “0” will be expected to sink 1.6 mA at a voltage below 0.8 V, requiring a pull-down resistor less than 500 ohms.
What is the maximum pull up resistor for a logic gate?
By knowing the information above, we can calculate the maximum pull-up resistor value required for a single TTL 74LS series logic gate as: Then using Ohms Law, the maximum pull-up resistance required to drop 3 volts for a single TTL 74LS series logic gate would be 150kΩ.
Is the external pull-up on reset really needed?
So there is no need to create an initial reset pulse externally. If there is not much external circuit and no long line on the reset pin, either a resistor or the capacitor should be enough. If you want to use debugwire there should be no capacitor. Posted by theusch: Tue.