To decrease the latency of accesses between the MPU L2 cache, and the two EMIF modules, a direct path between the MPU subsystem and the EMIFs is created. This direct path is supported by a memory adapter (MPU_MA) module. The MPU_MA splits the incoming (from L2 cache) AXI4 traffic into MPU_AXI2OCP and EMIF accesses. The MPU_AXI2OCP accesses are sent to the memory adapter A2O ports. The EMIF accesses are optionally interleaved between the two EMIF ports. Mandatory firewall checks are performed on all accesses to the EMIFs.
The main features of the MPU_MA are:
- Splits accesses between the MPU_AXI2OCP and the EMIF
- Input from L2 cache and output to MPU_AXI2OCP is AMBA4-compatible and runs at half the Cortex-A15 CPU frequency
- Supported read response interleaving on A2O port
- Parallel processing of reads and writes
- Support for narrow bursts
- Supports 4 × 128-bit line fills and eviction with critical word first
- Supports barrier instructions on normal read and write channels
- Direct 128-bit interfaces to each of EMIF1 and EMIF2:
- Single request multiple data
- No write response on posted writes
- Performs interleaving functions to load-balance the activities across the two EMIFs
- Uses firewall logic to check access rights of incoming addresses. The firewall on both EMIFs supports:
- Configurable number of regions with fixed priority
- Access support for up to eight execution domains
- Busy indicator during reconfiguration
- Blocked read and write access to the EMIF for all accesses failing authorization checks
- Burst wrap for single cache line fills
- Supports boot from EMIF space
- Supports 8 GiB of memory. 6GiB accessible only by the MPU (MPU-only memory) and 2GiB shared among the system. Only 4 GiB are physically available on this device. 2GiB accessible only by the MPU and 2 GiB shared among the system.
- MA_LSM supports programmable interleaving for 2 GiB of shared memory:
- Programmable multizone DRAM mapping and interleaving configuration
- Supports four prioritized sections for defining configuration regions within the external memory
- Supports interleaving at 128-, 256-, and 512-byte boundaries
- Fixed interleaving for extended 6 GiB of MPU-only memory
- Supports standard disconnect and idle protocols for independent powering down of the MPU_MA and both EMIFs (the EMIF must be powered down or up as a pair)
- Probe interface for performance monitoring of the EMIF ports
- 11 outstanding reads and 16 outstanding writes
- Supports exclusive accesses used for MPU internal synchronization
- Provides watchpoint capability on AXI bus. For more information, see Section 4.3.4.7.
Figure 4-6 shows the integration of the MPU_MA in the device.