High imped is used in TA of ethernet MDIOread transaction ?

[rakesh_aadhimoolam]

Can someone explain me this.
it is very urgent.
what is the importance of high impedance in read transaction
why high impedance is used only in read transaction and not in write transaction.

"The turnaround time is a 2 bit time spacing between the Register Address field and the Data field of a management frame to avoid contention during a read transaction. For a read transaction, both the STA and the PHY shall remain in a high-impedance state for the first bit time of the turnaround. The PHY shall drive a
zero bit during the second bit time of the turnaround of a read transaction."

Thanks

 

[koggestone]

Re: High imped is used in TA of ethernet MDIOread transactio

basically u have only 1 STA , but Multiple PHYs

So during Write (STA writing) , there wont be any collisions since there is
only 1 STA. hence no need of high impedance.

during read (STA reading) , basically STA drives first (write) and then the
PHY drives (read) the wire . So during this handoff , to provide some safe margin
(so that both STA and PHY dont drive simultanously) , i guess there is
a brief period of high impedance.

(just like when 2 people are talking , there is brief moment of silence when
first person finishes talking , and the second person starts talking. if there is
no brief silence , then there will be that brief collision that screws up the
initial part of conversation)