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1000 Threads found on edaboard.com: Weak Pull Up
I don't think it is possible to disable the weak pullups on this micro. It is basically an 80C32, where the pullups are always on, to allow the I/O pins to function as both inputs and outputs, simply by clearing the port latch; there is no data direction register. Is it really that important to have the pullup disabled? (...)
Hi, I face some problems in designing a full CMOS SRAM cell: 1. The choose of W/L ratio The W/L of the back-to-back inverters should be the same? I saw this in somewhere. I was confuse by that because in a latch, the forward inverter should be stronger than the feedback inverter... The Wordline transistor should have smaller W/L com
Hi, I face some problems in designing a full CMOS SRAM cell: 1. The choose of W/L ratio The W/L of the back-to-back inverters should be the same? I saw this in somewhere. I was confuse by that because in a latch, the forward inverter should be stronger than the feedback inverter... The Wordline transistor should have smaller W/L compare
if you want 20 mA you need to set it to 'output' and assert a high on that pin.... the internal pull-up (weak pull-up) is only for 'input' mode on that pin... note also that if a pin can source 20mA all the pins can't source more than 100mA or all the ports more than 200mA (of course it depends on your microcontroller (PIC? AVR?), but (...)
Another question,usually,what's the internal pull-up resistor value can be called weak pull-up?
No, a weak pull-down is a large resistance (or equivalent, i.e. it might be an active device on a chip), as high a resistance as possible which overrides any leakage currents to guarantee a valid logic 0 voltage. Smaller values would waste power when driven high, higher values would not guarantee a logic 0.
No. The pull-up resistor only acts as a "weak" pull-up source. So when slave drives low, the net will be pulled-down to '0'. -------------------------------------------------------------------------------- You can also refer to the open-drain circuit.
Output state wouldn't be set through a weak-pull resistor, this has an effect only for input or bidir pins (also open-drain, of course). weak pull-up can be enabled in Pin Planner tool (with newer Quartus versions) or in assignment editor, also for group of pins with wildcard pingroup* syntax. As nearly everything you may (...)
1) im using the circuit below and when im connecting pull-up or pull down resistor the system not working ! , i know that PORTB in PIC18F4550 has internal resistors but even when i connect resistors to PORTD system in not working as it should be. "Not working" is in fact a vague information. I understand, that the circuit is intende
hi today i tried to build a simple program that turns on LED when a button is push, using weak pull-up feature list F=inhx8m, P=16F688, R=hex, N=0 #include P16F688.INC __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _PWRTE_ON & _MCLRE_OFF & _CPD_OFF & _BOD_OFF & _IESO_ON & _FCMEN_ON ;definitions --------------------------- ba
I am using PIC18F452 controller, in this i want to use PORTC to interface a compass. In the datasheet he mentioned PORTB has weak pull-up resistors, but he didn't mentioned anywhere about PORTC pull up resistors. Does PORTC have pull ups?
Hi, Prove it to yourself, if you have Mclre ON and leave Pin1 unconnected , the program may not run at all, or run on and off because that pin is floating. For that reason you must tie Pin1 to Vdd either direct or via a resistor, typically 10k, which is often used with a cap in a reset switch situation. I believe the weak internal pull up yo
The datasheet of a 16F877 says weak pullup current 50 to 400 uA at 5V which means the weak pullup can range from 12K5 to 100K. I often use them if I have to connect keys to a pic so I do not need any external resistor to +5V. If you do not enable the weak pullups the pin is floating if (...)
I have read some where that the pull up transistors should be weak...why is it so?
In PIC18F4550, only PORTB has internal weak pull-ups, the other ports don't. Hope this helps. Tahmid.
Port 0 has dynamical push-pull instead. Omitting weak pull-ups apparently seemed appropriate to the original 8051 designers. The detail has been copied with each 8051 compatible IO-port since 30 years. 8051 developers use to know this, or learn it later on.
hi, You can use 10K PU on those pins, do you know that PORTB has internal weak pull ups.? E
I am not sure if there will be any problem or not when i want to output_low when there is an pull-up resistor at output line? MCU=PIC16F1946 As I remember the PIC has internal weak pull-ups. you can maybe use them. Or use an external resistor like mentioned and explained in the datasheet of TPS25200.
Hi, I wonder if @lter@ family has internal pull-up, just like CoolRunner? Best Regards, ltg
Can anyone explain the pull-Up and pull-Down phenomenon? Especially if we are using microcontrollers or logic elements. I mean in which situations can we use them?Can you give an example
:D some ICs require their output pins to be connected with a pull-up resistor. i wonder what this is for. another Q, what does open drains mean? 8O
pic is different of 8051 . such as output, 8051 si TTL,but PIC is ST/TTL. usually,we add a pull up resistance. but who could tell me if i also add a "pull up resistance"with the PIC,what will happen? thank you!
Hi, Could you teach me how to determine the pull-up resistor value for I2C Bus? Thz
Hello all, I found there are several values of pull-up resistor, for example 1k, 3.3k, 4.7k. Is the value of resistor proportional to the VCC? Or it related to other parameters, such as current? Regards, DAVY
We use a pull up resistor to ensure that the CMOS input will recognize the high output of TTL...can someone explain to me what happens when the TTL output is high with some circuit analysis? I read somewhere " the effect of a TTL output on external circuits is negligible when the pin is pulled high by an external resistor" ...and i'm kinda confused
Does the MSP430F1121 reset pin have an internal pull-up resistor or is an external one required? Thanks
Hello pull-up/pull-down resistor pull-ups (or pull-downs) have two primary purposes both of which are variations on a fundamental theme which is to prevent a short-circuit by adding a resistor in the path between Vcc and GND for a particular signal. Configuration: Many ICs have pins which must be set to a HIGH or (...)
hello how can i setup internal pull-up resistors for ports of atmega16? for example how can i setup pull-up resistors for portA? only i must set ddra to 1 or it needs other wthings too? thank you
hi there, please help me, it said that the port 0 in 89s52 doesn't have internal pull up, what is internal pull up? please give me a clear explanation of internal pull up, thank you very much :)
hi, What is the typical value for a pull up or pull down resistor? IL be using this in Microcontroller GPIOs. tnx
Hi I wanted to created a top-level block that contains two 8-bit tristate buffers ,one is connected to the input of a register and the other is connected to the output ...I got this warning : WARNING:Xst:2042 - Unit zreg: 8 internal tristates are replaced by logic (pull-up yes): into1<0>, into1<1>, into1<2>, into1<3>, into1<4>, into1<5>, into1<6
Hi all: I download a data of download cable from Altera, I don't find that the 10-pin need connect to pull up resistance and pull down resistance, but somebody tell me that if CPLD has no pull up resistance and pull down resistance, it will not work. So I think I can get right idea from here, If there need (...)
Is it always better to use a pull up resistor on the CS active low input of an IC? Does it make a difference if the CS input is open drain/collector or not?
To our Smart Card ic product, when set pull up resistance to 100KΩ, it will reset, can not work. what cause this iusse?
I want to add a weak pull-down resistor on 3-state output buffers and bidirectional buffers in Xilinx FPGA, I have tried to code it like this: IOBUF KIO_0 (.O(KIO_I), .IO(KIO), .I(KIO_O), .T(!we)); IOBUF KIO_1 (.O(KIO_I), .IO(KIO), .I(KIO_O), .T(!we)); IOBUF KIO_2 (.O(KIO_I), .IO(KIO), .I(KIO_O), .T(!we)); IOBU
May be it's atrivial question but i didn't know it What is the use of the pull up resistance in input pins in the microcontroller from the electronic point of view?
If I remember correctly the diagram shown in 8051 book by K J Ayala, Port 0 does not have internal pull-up, whereas other ports have. Since you are planning to interface RAM, you will also need a Latch, So the Port0 pins will have to drive 2 loads. I suggest using a weak pull-ups, may be 33K !? - Vignesh
it is infact a weak pullup and is enabled only when the pin is configured for input.
If a 3.3 V output signal is driven to 5V logic,we add pull up resistor this instance is this related to rise time of the signal.Then how it is.Kindly clarify this
Can anyone help me out in determining the resistance values of pull up and pull down resistors that are being used for input and output pins. What are all the considerations needed to be taken into account?
can any one help me in selecting a pull up/pull down resistor value
Hi there, I am attaching a existing board on my new design... on New design I have given pullup to I2C bus (10K) for 3 devices... it worked fine.... but after attaching the existing board, I2C bus is not working... Existing board contains two I2C device with individual pull-up(10K) and 100pf grouding on the SDA/SCL signal...... Can an
why sometimes designers use 1KΩ resistor for pull-up and sometimes use 5.6KΩ? what is the concept of using differnt values of risistors in pull-up circuits? the same quastion for pull-down.
Plz clarify my doubt which is better pull up or pull down
hello every body i have some questions ...... what is meant by pull up in the Option reg. and if there are programs to design microcontroller circuits pleaz dont forgot me and thanks
hi Some materials said that we cansolve the bus'es stuck at fault problem by putting pull-up resistors on bus why? and also the practise can deal with the bus'es low power too. why? anyone can explain it for me? thanks drizzle
How to calculate the correct pull-up resistor value? how does my pull-up resistor affect the rise time of the signal? If i add a pull-up will there be variation in rise time and fall time and do i need to compensate it?
Hi, i am designing pull-up I/O used in battery system. who can offer me some solutions? thanks
why we need pull-up resistor? to control current flow? how it can help in maintaining the voltage?
I am new to VLSI , i had doubt on pull-up and pull-down ......can anyone help me?