I2C Protocol Quiz

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Questions and Answers

What is the purpose of the SDA line in the I2C protocol?

  • To transmit data to or from target devices. (correct)
  • To power the target devices.
  • To control the direction of data flow.
  • To provide a clock signal for data transfer.

Which of the following statements about the SCL line in the I2C protocol is true?

  • SCL is used to synchronize data transfer. (correct)
  • SCL is used to power the controller device.
  • SCL is used to transfer data bits.
  • SCL is controlled by the target device.

What is the purpose of a pullup resistor in an I2C communication?

  • To provide a path for the SDA and SCL lines to ground.
  • To prevent the SDA and SCL lines from experiencing voltage drops during data transmission.
  • To limit the current on the SDA and SCL lines.
  • To ensure a high logic level on the SDA and SCL lines when no device is driving them. (correct)

How many lines are used for communication in the I2C protocol?

<p>Two (B)</p> Signup and view all the answers

What is the relationship between the pullup resistor size, the pull-down current, and the minimum pullup resistance?

<p>The minimum pullup resistance is inversely proportional to the pull-down current. (B)</p> Signup and view all the answers

What is the relationship between the pullup resistor size and the rise time of the SDA and SCL lines?

<p>Larger pullup resistors result in slower rise times. (B)</p> Signup and view all the answers

What is the primary function of the controller device in an I2C communication?

<p>All of the above. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of the I2C protocol?

<p>Full-duplex communication. (C)</p> Signup and view all the answers

What factors should be considered when selecting a pullup resistor for an I2C communication?

<p>The pull-down current of the connected devices, the rise time required for the SDA and SCL lines, and the capacitance of the bus. (A)</p> Signup and view all the answers

What is the purpose of the I2C protocol?

<p>To transmit data over a serial bus using two wires. (D)</p> Signup and view all the answers

What are the two wires used in the I2C communication protocol?

<p>SDA and SCL (C)</p> Signup and view all the answers

What type of communication is used by the I2C protocol?

<p>Half-duplex. (A), Synchronous. (C)</p> Signup and view all the answers

Which of the following is an example of a target device that can be used in an I2C communication?

<p>Digital-to-Analog Converter (DAC). (A)</p> Signup and view all the answers

What is the maximum transmission rate for the I2C protocol?

<p>It depends on the specific implementation. (D)</p> Signup and view all the answers

What is the purpose of the SMBus® trademark?

<p>A trademark related to I2C communication. (C)</p> Signup and view all the answers

What happens when voltage levels are mismatched between an I2C controller and a target device?

<p>Mismatched voltages can disrupt communication or damage a device. (A)</p> Signup and view all the answers

Which statement is true regarding the SCL and SDA lines in an I2C bus?

<p>They have specific characteristics outlined in the device data sheets. (C)</p> Signup and view all the answers

What role do pullup resistors play in I2C communication?

<p>They determine the input voltage levels for the connected devices. (B)</p> Signup and view all the answers

What must be considered when designing systems with multiple power sources and voltages?

<p>Voltage level translation is crucial to ensure compatibility. (D)</p> Signup and view all the answers

In the provided example, if the controller and pullups are set to 3.3 V, what potential issue arises with a target device set to 5.0 V?

<p>The controller may underdrive the input of the target device. (D)</p> Signup and view all the answers

What represents a logical one in I2C communication?

<p>SDA releases the line, letting the pullup resistor bring it high. (D)</p> Signup and view all the answers

Which action signifies a logical zero in the I2C protocol?

<p>SDA pulls the line down toward ground. (D)</p> Signup and view all the answers

What does a change in the SDA line during the SCL pulse indicate?

<p>A START or STOP condition. (D)</p> Signup and view all the answers

In I2C communication, what is the purpose of the address frame?

<p>To identify the target device before sending data. (D)</p> Signup and view all the answers

What does each data frame in I2C consist of?

<p>One byte of data and an acknowledgment bit. (D)</p> Signup and view all the answers

How does the I2C protocol signify the beginning of communication?

<p>By the controller device sending a START condition. (C)</p> Signup and view all the answers

What occurs after the address frame in I2C communication?

<p>One or more data frames follow. (C)</p> Signup and view all the answers

What signal is used to time the sequence of bits in I2C communication?

<p>SCL. (A)</p> Signup and view all the answers

What is the role of the second byte when a hardware controller cannot transmit to a target address?

<p>It identifies the controller to all devices on the system. (B)</p> Signup and view all the answers

What is a consequence of a microprocessor not having a built-in I2C controller?

<p>It must poll the SDA and SCL lines to monitor communications. (B)</p> Signup and view all the answers

What does the START byte represent in I2C communication?

<p>A read from I2C address 00. (C)</p> Signup and view all the answers

Why is address 01 reserved in I2C protocol?

<p>To facilitate the C-Bus protocol on the I2C bus. (A)</p> Signup and view all the answers

What happens when the target device detects a zero during the START byte?

<p>The device switches to faster polling to detect the next I2C transmission. (D)</p> Signup and view all the answers

What is addressed by I2C address 02?

<p>It facilitates communication between different bus formats. (A)</p> Signup and view all the answers

What effect does the use of a START byte have on the target device's polling rate?

<p>It allows the target device to poll at a slower rate initially. (D)</p> Signup and view all the answers

Which scenario is most likely if a controller is unable to send its commands to a target device?

<p>The controller must identify itself using a second byte. (D)</p> Signup and view all the answers

What will be the resulting SCL if Controller 1 pulls SCL low and Controller 2 does not pull it low?

<p>SCL will go low (B)</p> Signup and view all the answers

During a competing bus claim, which controller's action dictates the state of SCL if both attempt to pull it low?

<p>The controller that pulls SCL low first (C)</p> Signup and view all the answers

In a situation where Controller 1 releases SCL to go high, what happens if Controller 2 continues to hold SCL low?

<p>SCL will stay low (C)</p> Signup and view all the answers

What remains true about SCL during multiple controllers contesting for the bus?

<p>SCL will remain low until all controllers release it (A)</p> Signup and view all the answers

What does a high-to-low transition on SCL signify during a START condition?

<p>A collision for bus access is occurring (D)</p> Signup and view all the answers

If Controller 1 finishes its operation and releases SCL, how is it affected by Controller 2's status?

<p>SCL will always remain low if Controller 2 is active (B)</p> Signup and view all the answers

Which of the following describes SCL during the bus claiming process if both controllers attempt to take control?

<p>SCL will be held low by the slower controller (C)</p> Signup and view all the answers

What is a primary function of the wired-AND connection in the context of SCL?

<p>To synchronize clock signals between multiple controllers (A)</p> Signup and view all the answers

Flashcards

I2C

A two-wire serial communication protocol with SDA and SCL lines.

SDA

Serial Data Line used in I2C for data transmission.

SCL

Serial Clock Line that synchronizes data transmission in I2C.

Pullup Resistor

A resistor that pulls a line to a high voltage when not driven.

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Pull-Down Current

Current that helps to pull a line to ground (low voltage).

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Bus Capacitance

The capacitance present in I2C wiring that can affect speed.

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Maximum Transmission Rates

The highest speeds at which data can be sent in I2C.

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Reserved I2C Addresses

Specific addresses set aside for special purposes in I2C communication.

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Half-Duplex

Communication where only one device sends data at a time.

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Full-Duplex

Communication allowing simultaneous sending and receiving of data.

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Controller Device

Device that controls communication on the I2C bus.

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Target Device

Device that receives or sends data on the I2C bus.

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DAC and ADC

DAC converts digital data to analog; ADC converts analog to digital.

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I2C Communication

A protocol for serial communication using one data line (SDA) and a clock line (SCL).

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Logical One

A state in I2C where SDA releases the line, pulled high by a resistor.

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Logical Zero

A state in I2C where SDA pulls the line to a low level near ground.

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SCL in I2C

The serial clock line that times the bit sequences in I2C communication.

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START Condition

Initiation of communication in I2C that signals a new frame is beginning.

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STOP Condition

A signal in I2C that indicates the end of communication.

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Address Frame

The first frame sent after a START, containing the 7-bit address and R/W bit.

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Data Frame

A frame that follows the address frame, consisting of one byte of data.

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I2C Voltage Levels

The specific voltage range for high and low signals in I2C communication.

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Voltage Level Translation

Adjusting voltage levels to ensure compatibility between devices in I2C systems.

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Impact of Mismatched Voltages

Unmatched voltages can cause communication failure or damage to devices in an I2C setup.

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Pullup Resistor Role

Determines output voltage behavior, influencing how devices interact in I2C.

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Device Data Sheets

Documents detailing characteristics necessary for correctly setting up I2C devices.

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Second Byte

Used to send the controller address to recognize devices in the system.

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Start Byte

A byte indicating the beginning of communication, typically when reading from address 00.

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Polling

The method a microprocessor uses to check the SDA and SCL lines for communication.

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Fast Rate Polling

A quick checking method used after detecting a Start Byte.

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Reserved Addresses

Specific I2C addresses set aside for particular protocols or formats.

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C-Bus Protocol

A reserved address in I2C for home and building automation devices.

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Wired-AND Connection

A circuit configuration where multiple devices can pull a line low, but not high.

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SCL Behavior during START

SCL stays low until the last controller releases its pull after a START condition.

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START Condition in I2C

A signal indicating that a controller wants to start communication on the bus.

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Clock Synchronization

The process ensuring that SCL signals are aligned between multiple controllers.

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Controller Competition for Bus

When multiple controllers try to access the I2C bus at the same time.

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Release of SCL

The action of a controller allowing SCL to return to high after communication.

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Importance of SCL State

The SCL line must remain low as long as any controller holds it down during competition.

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Monitor SCL

A controller's action to check the state of SCL before sending data.

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Study Notes

I2C Overview

  • I2C is a common communication protocol used in various TI products
  • It enables communication between microcontrollers and peripheral devices
  • The protocol is simple and cost-effective for device manufacturers
  • It uses two lines for communication: SDA (serial data) and SCL (serial clock)

I2C Physical Layer

  • I2C systems use two shared communication lines (SDA and SCL) for bidirectional, half-duplex communication
  • Pull-up resistors are needed on both lines
  • The physical layer implements open-drain connections on SDA and SCL
  • Open-drain connections enable non-destructive bus contention

I2C Protocol

  • Communication begins with an I2C START condition
  • The I2C controller claims the bus, pulling SDA low and then SCL low
  • When communication is complete, a STOP condition is issued, causing SCL to be released high and then SDA to be released high
  • Data transmission uses a sequence of logical ones and zeros
  • A logical one occurs when the SDA line releases, pulling high by the pull-up resistor
  • A logical zero occurs when SDA pulls down to a low level

I2C Examples

  • Examples use DAC80501 (digital-to-analog converter) and ADS1115 (analog-to-digital converter)
  • I2C is used for writing and reading data
  • I2C communication involves multiple bytes, starting with the address byte
  • An acknowledge (ACK) bit confirms successful communication

Reserved Addresses

  • Not all possible 7-bit addresses can be used (reserved addresses)
  • Reserved addresses are used for specific purposes or future use cases
  • Some devices use 10-bit addressing to increase the possible addresses

Advanced Topics

  • Clock synchronization and arbitration are crucial for multiple devices on the same bus
  • Clock stretching allows a target device to control the clock rate in certain situations
  • Pull-up resistor sizing is critical for I2C bus speed
  • Voltage levels must be compatible between devices. Improper voltage matching can damage the devices

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Related Documents

A Basic Guide to I2C PDF (Texas Instruments)

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