A signalling standard typically used in buses that either drives the wire low, drives the wire high or disconnects from the wire (Hi-impedance, Hi-Z or tri-stated) such that there will not be a driver conflict when the wire is driven by another unit/driver. Two low impedance drivers driving to different levels (High Vs. Low) can potentially damage each other but certainly will corrupt the data on the wire. Allows for shared wires (with coordination).
Questions tagged [tri-state]
111 questions
10
votes
6 answers
What is the purpose of a tri-state pin in a Oscillator
I'm trying to interface this clock (32.768kHz Ceramic
Surface Mount Crystal Oscillator datasheet), but I'm confused as to what to do with the tri-state pin. What is it's purpose in the oscillator and should I care about it? Can I just leave it…
jack sexton
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votes
5 answers
How can I read a tristate output with microcontroller?
I'd like to interface the STAT line of an MCP73831 lithium ion charge manager IC to a microcontroller to read the current charging status of it.
The datasheet explains, in the section 5.2.1, that the STAT line is tristate output and have the…
RHaguiuda
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9
votes
5 answers
Does ISA bus (or PC/XT bus) have some means of arbitration to resolve bus contention?
My understanding of ISA bus is that the CPU places an address on the bus and any expansion card is free to respond to that address by taking control of the data bus. I presume that tri-state buffers are used. So my question is, are there any…
Chris_F
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8
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4 answers
Tri-state output to three analogue levels?
Is there a circuit which can transform a tri-state (low, high-Z, high) output to three voltage levels?
Ideally, the circuit will use only passives and diodes.
Would a simple voltage divider across the pin do the job?
Vdd
…
fadedbee
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7
votes
5 answers
Reasons for having MCU pin-states default to pull-up/down out of reset
On many MCUs, pin-states default to tri-stated (a.k.a. analog inputs) when the MCU resets so as to not affect the circuits they are connected to until software configures the pins. The tri-stated pins also allow the HW designer to choose the pull…
TRISAbits
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6
votes
1 answer
Is my SPI multiplexing design correct?
I want a RPi to act as a SPI master and be able to communicate with 24 SPI slaves. The SPI connection is full-duplex. The SPI slaves are about 50 cm away from the master (SPI runs on wires to an other PCB board not considered here).
The 24 slaves…
Victor Lamoine
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6
votes
5 answers
Will multiple chips outputing onto a bus for a few nanoseconds cause damage?
I'm working on a home-brew CPU design, with the usual mix of parallel EEPROMs, static RAMs and registers, tri-stated onto a single 8 bit bus.
My /output-enable logic for three tristate-able chips on the databus is:
/Ken = /a
/Ren = /a nor /b
/Men =…
fadedbee
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5
votes
4 answers
How can I differentiate between high and high-Z state?
I'm using this MCP73831 device.
I want to know how what to expect as a voltage level on the STAT pin when the below chart on page 13 says, STAT = HIGH & STAT = HIGH-Z.
When the charging is completed, I need to see HIGH voltage (say if Vdd is 5V,…
user220456
5
votes
2 answers
Logic Levels between 5(V) and 3.3(V) devices
I am using a 5V microcontroller to communicate with a Bluetooth module operating at 3.3V.
I have regulated the output from the 5V microcontroller rail to 3.3V rail for the Bluetooth module.
Since I am using a UART, I need to use a TX pin to go to…
Edwin
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5
votes
6 answers
Why do I2C lines use open drain driver instead of tri-state drivers?
My understanding is that I2C lines use pull-up resistors to passively pull up the bus to logic high because the drivers used on the bus are active drivers, namely open collector/open-drain. Since open collector/open-drain drivers can drive the line…
athedcha
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8 answers
Tristate and having low and high at the same time
I am reading about microcontrollers now and i ve been confused.
I am reading some pdfs and there is a symbolism of tristate condition High->High/Low. Meaning going from High to high and low at the same time. How can this be possible?? what is the…
Nick Alexis
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5
votes
1 answer
Simple way to invert a tristate output
I am looking for a simple circuit to invert a tristate output from a microcontroller, hopefully using only BJTs. What I mean by this is that the truth table would look like:
IN OUT
H L
L H
Z Z
An ordinary inverter circuit / NOT gate…
Sean Purser-Haskell
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4
votes
2 answers
How to wire output buses together
Say I instantiate a parametrized number instances in an array and each of these instances produces an 8-bit output value if it is selected. What would be the best way to wire these outputs together?
I currently use tri-state buffers as in the…
mtvec
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4
votes
3 answers
MCP73831: design a lithium battery charging circuit
I am trying to design a charging circuit for a lithium polymer battery with 2200 mAh capacity and 3.7 V nominal voltage. The integrated circuit for the control of the charge of the battery is the MCP73831 and as a power supply a solar panel of 6.2…
FranMartin
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3 answers
Can one tri-state pin drive two SS pins?
This is how i see it;
State H: SS out is High, Deselecting SS 2, turning off Q2 and on Q1, which grounds SS 1, turning it on.
State L: SS out is Low, turning off Q1 and grounds SS 2 through Q2. SS 1
is deselected by R1
State Z: SS out is high…
Alexander M
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