Altera Cyclone V Device Handbook page 572

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Dynamic Mapping Mode

In dynamic mode, every unique input ID that is received from the L3 master port is assigned to an unused

output ID. The new output ID is applied to the transaction as it is issued to the ACP slave of the SCU. Any

transaction that arrives to the ACP ID mapper with an input ID that matches an already-in-progress

transaction is mapped to the same output ID. Once all transactions on an ID mapping have completed, that

output ID is released and can be used again for other input IDs.

Fixed Mapping Mode

In fixed mode, output IDs 2 through 6 can be assigned by software to a specific 12-bit input ID. This ability

makes it possible to use the lock-by-master feature of the L2 cache controller, because the input transaction

ID from the master is always assigned to a specific output ID. Unlike dynamic mode, ID 7 is not available

for fixed mapping because it is reserved for dynamic mode only to avoid system deadlocks.

The ACP ID mapper has two banks of registers to control the behavior of the mappings, namely, a request

bank and a read-only status bank. Both banks contain the same number of registers. To change the settings

for a particular mapping (either a specific fixed ID, or all dynamic mappings), software should write to the

appropriate register in the request bank. The hardware examines the request, and only applies the change

when safe to do so, which is when there are no outstanding transactions with the output ID. When the change

is applied, the status register is updated. Software should check that the change has actually taken place by

polling the corresponding status register.

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Cortex-A9 Microprocessor Unit Subsystem

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