which factors effecting the communication protocol speed

[chandu.kurapati]

Hi,
Generally in any communication protocol (I2C, SPI, CAN etc..) mentioned like max & min speeds in some mbps (or) kbps.

That speeds mostly vary from one protocol to another protocol, on which factors speed of the protocol decided, which factors effect the speed of the protocol & how it effect.

can any one explain about it brief...

 

[betwixt]

it brief...

The rise and fall time of the signal edges, which is determined by the properties or the cables/wiring and loading on the the driver. For example, in I2C, the SCL SDA wires are only pulled up by passive components, resistors in that case, so the capacitance of the cable and components attached to it makes an RC filter and limits the rise and fall time of the waveform. It the edges are slow to rise and fall, the transition between logic levels becomes more prone to jitter and the width of pulses changes. As the speed increases, the problem worsens to the point where data can no longer be reliably carried. At very high speed, the inductance, cross-coupling and even propagation delay also has more effect and can limit the speed.

Brian.

 

[chandu.kurapati]

Hi betwixt,

Can you explain how exactly R,L,C components effect the raise and fall time of the signal.
please explain with some example (or) share some related data for me.

 

[betwixt]

Basic time constant theory. Look up RC time constant and you will see lots of explanations of capacitors charging and discharging through resistors. Imagine the voltage is your data and the capacitor is the capacitance of your cable and all the components attached to it in parallel. In the case of I2C, the resistor is the pull-up resistance on the clock and data lines and in other protocols it is the output resistance of the device driving the line.

Brian.