How Does SPI Determine the Starting Point of Data Transmission?

  • Thread starter Thread starter themagiciant95
  • Start date Start date
  • Tags Tags
    Interface Serial
Click For Summary

Discussion Overview

The discussion revolves around the operation of the Serial Peripheral Interface (SPI) protocol, specifically focusing on how the starting point of data transmission is determined. Participants explore aspects related to clock signals, data lines, and the concept of common ground in SPI communication.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions how the SPI system identifies the starting point of data transmission, noting that both MOSI and MISO lines have a default state of "1" which could be misinterpreted as data.
  • Another participant asserts that the clock signal only operates when there is a byte to transmit, referencing a specific section of a technical document for clarification.
  • A participant draws a comparison to the UART protocol, expressing confusion about the necessity of a common ground in SPI, as it is not explicitly shown in the SPI diagram.
  • Another participant responds to the common ground question, suggesting that it is implicitly understood to be present in the SPI diagram, even if not depicted.

Areas of Agreement / Disagreement

The discussion contains multiple viewpoints regarding the starting point of data transmission and the role of common ground in SPI. There is no consensus on these issues, as participants express differing understandings and interpretations.

Contextual Notes

Some assumptions about the operation of SPI, such as the role of the clock signal and the implications of default states on data lines, remain unresolved. The discussion also highlights a potential misunderstanding of common ground in the context of SPI communication.

themagiciant95
Messages
56
Reaction score
5
I have a SPI with a master and a slave:
52ddb2dcce395fed638b4567.png
How the system knows what's the starting point of the data sent ? It's ok that we have the clock, but both MOSI and MISO have a default state on "1", that may be sampled as data sent
 

Attachments

  • 52ddb2dcce395fed638b4567.png
    52ddb2dcce395fed638b4567.png
    9.2 KB · Views: 881
Engineering news on Phys.org
Thanks. When i studied the UART protocol i read that it need a common ground:

file.png


In the SPI diagram it doesn't appear. Why ? Probably i don't clearly understand what a commond groud is... :(
 

Attachments

  • file.png
    file.png
    5.5 KB · Views: 525
themagiciant95 said:
In the SPI diagram it doesn't appear. Why ?

It is just implicit. They didn't bother to put it in the diagram, but it's there.
 
  • Like
Likes   Reactions: themagiciant95

Similar threads

How Should I Terminate and Route SPI Signals for Multiple External PCBs?
  • · Replies 2 ·
Replies
2
Views
5K
Understanding the SPI Interface: Clock, Data & Oscillators
  • · Replies 11 ·
Replies
11
Views
3K
Determining communication direction in SPI ports
  • · Replies 4 ·
Replies
4
Views
2K
High School Spy Extravaganza-Probability/Logic riddle
  • · Replies 1 ·
Replies
1
Views
1K
Graduate Project Progress Report and possible Radio Astronomy Technique?
  • · Replies 9 ·
Replies
9
Views
2K
Routing data from the Serial port to ICs
  • · Replies 19 ·
Replies
19
Views
7K
How to Determine the Unit Cell Type From the XRD Data?
  • · Replies 1 ·
Replies
1
Views
2K
Why is my PIC 18F2550 not sending data when I tell it to?
  • · Replies 6 ·
Replies
6
Views
2K
How to Integrate a Counter in a Data Transmission Circuit?
  • · Replies 2 ·
Replies
2
Views
3K
Digital signal interface to computer
  • · Replies 6 ·
Replies
6
Views
4K