ARM NIC-301 User Manual

Page of 54
Functional Description 
ARM DDI 0397G
Copyright © 2006-2010 ARM. All rights reserved.
2-18
ID031010
Non-Confidential
all outstanding write transactions with the same ID go the same destination.
When the slave interface receives a transaction:
if it has an ID that does not match any outstanding transactions, it passes the CDAS
if it has an ID that matches the ID of an outstanding transaction, and the destinations also 
match, it passes the CDAS
if it has an ID that matches the ID of an outstanding transaction, and the destinations do 
not match, it fails the CDAS check and is stalled.
A stalled transaction remains stalled until one of the rules passes. For complex infrastructures, 
it might be necessary to configure an additional rule for write transactions.
Note
 This is only for the single-slave-per-ID CDAS configured slave interfaces.
The extended write rule ensures that if single-slave-per-ID rules are passed, then the network 
only issues a write transaction to a new destination if all the outstanding write transactions have 
had the last write data beat transmitted.
The AMBA Designer tool automatically detects when this is required. See Additional reading 
on page viii
.
2.3.6
Lock support
You set support for locked transaction for masters and slaves at configuration time. The AMBA 
Network Interconnect infrastructure is configured for lock support into all switch master 
interfaces that are required to provide lock support for all the relevant masters and slaves in the 
system. See Lock transactions on page 2-7 for information on the scope of lock support for 
AHB-Lite slave interfaces.
At a switch master interface with lock support, logic exists that:
Stalls a locked transaction after it is arbitrated.
Note
 
If a co-incident transaction exists on the other address channel, it is not stalled unless it is 
a lock transaction.
Stalls the other address channel.
Permits all the outstanding transactions to complete.
Enables the locking transactions source read and write channels when there are no 
outstanding transactions.
Enables all sources for arbitration, and normal operation continues when an unlocking 
transaction completes.
When the network receives a locking transaction, if there is a co-incident lock transaction 
on the other address channel, then the read always takes priority, and the write address 
transaction is stalled.