2.5 System address conversion
This section describes how the DMC-520 transforms the system address to the SDRAM address.
The following figure shows the functions that the DMC-520 uses to transform the address
that it receives from the system to the address it presents to the SDRAM.
Figure 2-4 System address conversion
The following describes the function of the boxes:
- Address map
- Receives the system address and converts it
to a suitable form for the Address decode function.
- TrustZone decode
- Decodes invalid address regions.
- Address decode
- Translates its input address to row, rank, bank, and column
A transaction is rejected in
the following circumstances:
- The transaction fails the TrustZone
- If Memory Map translation is enabled, the
transaction targets a reserved address region. See
Principles of ARM®
Memory Maps White Paper.
- The transaction targets a physical rank that
is masked by the Rank mask function.
- The transaction, or decoded address, falls above the
allocated DRAM space.
A rejected transaction has no effect on memory. If a
transaction is rejected then write data is ignored and read data is
returned as zero. Rejected transactions might be given a non-data
error response based on the setting of the enable_err_response* bits
in the memory_address_max_31_00* registers. A PMU signal reports
any failed transactions. It is up to the system to prevent
Non-secure masters form determining information about failed Secure
transactions using the PMU signals.