When do you need a pull-up resistor?

A pull-up resistor may be used when interfacing logic gates to inputs. For example, an input signal may be pulled by a resistor, then a switch or jumper strap can be used to connect that input to ground. This can be used for configuration information, to select options or for troubleshooting of a device.

What is the need of pull up and pull-down resistor for GPIO lines?

When the GPIO voltage level is low, then it is in high or high impedance state, then the pull up and pull-down resistors are used to ensure GPIO which is always in a valid state. Usually, the GPIO is arranged on a microcontroller as I/O.

Does JTAG need pullup resistor?

You must ensure that your board has appropriate pull-up and pull-down resistors on the JTAG signals: TMS, TDI, TDO, nSRST and nTRST must have pull-ups.

Which port need pull up resistors?

Port 1, 2 and 3 have internal pull-up resistor. Port 0 is in tri-state condition and we have to connect external pull-up resistor to remove that condition.

How do you determine the pull-down resistor value?

To calculate the pull-down resistor value, it’s slightly different from the pull-up resistor value. Knowing that current is 100uA, we’ll take 0.5v as our pull-down voltage since the input is 0.8v. Thus, applying our R = V/I once again, but this time we don’t have to minus, so our formula remains constant.

When do you use pull up and pull-down resistors?

Pull-up and pull-down resistors are often used when interfacing a switch or some other input with a microcontroller or other digital gates. Most microcontrollers have built-in programmable pull-up and/or pull-down resistors, so fewer external components are needed.

Why do we need a pull-down resistor?

What is Pull-down Resistors. Similarly to pull-up resistors, pull-down resistors ensure the voltage between VCC and a microcontroller pin is actively controlled when the switch is open. However, instead of pulling a pin to a high value, such resistors pull the pin to a low valued instead.

When do you use pull-up and pull-down resistors?

Is JTAG push pull?

Although Virtex JTAG ports have internal pull-ups that are connected by default on TDI and TMS, Xilinx suggests using the external pull-ups to ensure that the device does not enter Boundary Scan mode. It is not necessary to place a pull-up resistor on TCK or on the output TDO; they can be left floating.

How do you determine the pull down resistor value?

What is a pull up pull down resistor?

Pull-up Resistor Summary A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH. A pull-down resistor connects unused input pins (OR and NOR gates) to ground, (0V) to keep the given input LOW.