Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK Datenbogen

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SAM9M10 [DATASHEET]

6355F–ATARM–12-Mar-13

The translation table walk hardware is a logic that traverses the translation tables located in physical memory, gets
the physical address and access permissions and updates the TLB.

The number of stages in the hardware table walking is one or two depending whether the address is marked as a
section-mapped access or a page-mapped access.

There are three sizes of page-mapped accesses and one size of section-mapped access. Page-mapped accesses
are for large pages, small pages and tiny pages. The translation process always begins with a level one fetch. A
section-mapped access requires only a level one fetch, but a page-mapped access requires an additional level two
fetch. For further details on the MMU, please refer to chapter 3 in ARM926EJ-S Technical Reference Manual.

The MMU generates an abort on the following types of faults:

• Alignment faults (for data accesses only)

• Translation faults

• Domain faults

• Permission faults

The access control mechanism of the MMU detects the conditions that produce these faults. If the fault is a result
of memory access, the MMU aborts the access and signals the fault to the CPU core.The MMU retains status and
address information about faults generated by the data accesses in the data fault status register and fault address
register. It also retains the status of faults generated by instruction fetches in the instruction fault status register.

The fault status register (register 5 in CP15) indicates the cause of a data or prefetch abort, and the domain num-
ber of the aborted access when it happens. The fault address register (register 6 in CP15) holds the MVA
associated with the access that caused the Data Abort. For further details on MMU faults, please refer to chapter 3
in ARM926EJ-S Technical Reference Manual.