ARM AMBA NIC-301 - Manual (Page 33)

Functional Description
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• 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.