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
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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 addresses.


A transaction is rejected in the following circumstances:
  • The transaction fails the TrustZone permission check.
  • 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.
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