Cyclone® V Hard Processor System Technical Reference Manual

ID 683126
Date 8/28/2023
Public
Document Table of Contents

10.4.2.5. Fixed Mapping Mode

In fixed mode, output IDs 2 through 6 can be assigned by software to specific 12-bit input IDs. 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. ID 7 is not available for fixed mapping because it is reserved for dynamic mode only to avoid system deadlocks.

The ACP ID mapper can control the behavior of read and write virtual fixed ID mappings through the vid*rd and vid*wr registers. By programming the force bit to 0x1 in the vid*rd and vid*wr registers, the 12-bit mid field is forced to a specific 3-bit virtual ID. The mid field can be different between the read and write AXI Master Mapping registers. When these registers are programmed, 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.