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Related Information
Functional Description—HPS Memory Controller
ACP ID Mapper
The ACP ID mapper is situated between the level 3 (L3) interconnect and the MPU subsystem ACP slave.
It is responsible for mapping 12-bit Advanced Microcontroller Bus Architecture (AMBA
®
) Advanced
eXtensible Interface (AXI
™
) IDs (input IDs) from the L3 interconnect to 3-bit AXI IDs (output IDs) supported
by the ACP slave port.
The ACP ID mapper also implements a 1 GB coherent window into 4 GB address space.
Functional Description
The ACP slave supports up to six masters. However, custom peripherals implemented in the FPGA fabric
can have a larger number of masters that need to access the ACP slave. The ACP ID mapper allows these
masters to access the ACP.
The ACP ID mapper resides between the interconnect and the ACP slave of the MPU subsystem. It has the
following characteristics:
• Support for up to six concurrent ID mappings
• 1 GB coherent window into 4 GB MPCore address space
• Remaps the 5-bit user sideband signals used by the Snoop Control Unit (SCU) and L2 cache.
For more information about AXI user sideband signals, refer to the CoreLink Level 2 Cache Controller L2C-
310 Technical Reference Manual, which you can download from the ARM website (infocenter.arm.com).
Related Information
ARM Infocenter (www.infocenter.arm.com)
Implementation Details
The ACP is accessed by masters that require access to coherent memory. The ACP slave port can be accessed
by the master peripherals of the L3 interconnect, as well as by masters implemented in the FPGA fabric (via
the FPGA-to-HPS bridge).
The ACP ID mapper supports the following ID mapping modes:
• Dynamic mapping
• Fixed mapping
Software can select the ID mapping on a per-ID basis. For input IDs that are configured for fixed mapping,
there is a one-to-one mapping from input IDs to output IDs. When an input ID is configured for dynamic
mapping, it is automatically mapped to an available output ID. The dynamic mode is more flexible because
the hardware handles the mapping. The hardware mapping allows you to use one output ID for more than
one input ID. Output IDs are assigned to input IDs on a first-come, first-served basis.
Out of the total of eight output IDs, only six are available to masters of the L3 interconnect. The first two
output IDs (0 and 1) are dedicated to the Cortex-A9 processor cores in the MPU subsystem, leaving the last
six output IDs (2-7) available to the ACP ID mapper. Output IDs 2-6 support fixed and dynamic modes of
operation while output ID 7 supports dynamic only.
Cortex-A9 Microprocessor Unit Subsystem
Altera Corporation
cv_54006
ACP ID Mapper
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2013.12.30