what is the advantage of exclusive access in AXI?

[krishanu007]

what is the benefit of exclusive access if another master can access it in between a exclusive access period of read & write? and the previous will be signaled error...!!!
how its becoming a atomic access???

 

[ckshivaram]

The basic process for an exclusive access is:
1. A master performs an exclusive read from an address location.
2. At some later time, the master attempts to complete the exclusive operation by performing an exclusive write to the same address location.
3. The exclusive write access of the master is signalled as:
• Successful if no other master has written to that location between the read and write accesses.
• Failed if another master has written to that location between the read and write accesses. In this case the address location is not updated.

 

[krishanu007]

The basic process for an exclusive access is:
1. A master performs an exclusive read from an address location.
2. At some later time, the master attempts to complete the exclusive operation by performing an exclusive write to the same address location.
3. The exclusive write access of the master is signalled as:
• Successful if no other master has written to that location between the read and write accesses.
• Failed if another master has written to that location between the read and write accesses. In this case the address location is not updated.

thank u a lot for trying to help me but this isnt what I asked..
You have told the procedure.
but what is benefit out of that if another master can break the exclusive access by just writing in.
which is not in the case of locked access.which obviously have its benefits.
the what exclusive access is offering over normal access??

 

[sudhamahesh70]

The main advantage of exclusive access is the master can have latest information of the register/memory (read transaction) and it will perform a write, like read-modify-write style....

 

[krishanu007]

The main advantage of exclusive access is the master can have latest information of the register/memory (read transaction) and it will perform a write, like read-modify-write style....

Hi sudha,
Isnt it correct that the same thing can be done via normal access.(read-modify-write back).
Why there is this dedicated functionaly and what it is offering over the normal (read-modify-write back) access.

 

[kbkdec15]

HI krishanu ,


have you got complete concept about Exclusive Access. Please clearify me about Exclusive access.

please update this topic

 

[bhadanisandip]

Now consider a system in which two AXI master devices are using same memory or we can say in technical term using shared memory. And as a system designer you always will make sure that at a time your one master does not overwrite your memory written by another master.

Consider AXI Master 1 (M1) has initiated exclusive read transaction for address location 12'h100 to 12'h10F. Now slave will start monitoring these addresses for ARID given by M1. Now till exclusive write operation is performed slave monitors that address and if that address is changed by another master M2 it will give indication of exclusive access failure during the exclusive write transaction and memory is dose not get updated by M1.

What happened in above scenario is that Slave has reserved some memory resource for M1 virtually by given exclusive read request from master. When master comes for write transaction for that memory location slave will allow to write that memory resource if only if another master device is not using that memory resource other wise data is not written to memory resource.

This way we can avoid memory overwrite problem for shared memory using EXCLUSIVE Access in AXI.



I have directly written advantage of EXCLUSIVE ACCESS in AXI to know more how Exclusive Access in AXI works please visit page given below.
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