Atmel Evaluation Kit AT91SAM9X35-EK AT91SAM9X35-EK Data Sheet

281

SAM9X35 [DATASHEET]

11055E–ATARM–10-Mar-2014

All the Masters can normally access all the Slaves. However, some paths do not make sense, such as allowing access
from the USB Device High speed DMA to the Internal Peripherals. Thus, these paths are forbidden or simply not wired,
and shown as “–” in the following table.

The Bus Matrix provides one decoder for every AHB master interface. The decoder offers each AHB master several
memory mappings. Each memory area may be assigned to several slaves. Booting at the same address while using
different AHB slaves (i.e., external RAM, internal ROM or internal Flash, etc.) becomes possible.

The Bus Matrix user interface provides the Master Remap Control Register (MATRIX_MRCR), that performs remap
action for every master independently.

The Bus Matrix provides some speculative bus granting techniques in order to anticipate access requests from masters.
This mechanism reduces latency at first access of a burst, or single transfer, as long as the slave is free from any other
master access, but does not provide any benefit as soon as the slave is continuously accessed by more than one master,
since arbitration is pipelined and has no negative effect on the slave bandwidth or access latency.

This bus granting mechanism sets a different default master for every slave.

At the end of the current access, if no other request is pending, the slave remains connected to its associated default
master. A slave can be associated with three kinds of default masters:



No default master



Last access master



Fixed default master

To change from one type of default master to another, the Bus Matrix user interface provides the Slave Configuration
Registers, one for every slave, that set a default master for each slave. The Slave Configuration Register contains two
fields: DEFMSTR_TYPE and FIXED_DEFMSTR. The 2-bit DEFMSTR_TYPE field selects the default master type (no

X

X

X

X

X

X

X

X

X

X

X

X

X

X

–

–

–

–

–

–

X

X

–

X

–

–

–

–

–

–

X

X

–

–

–

–

–

–

–

–

X

X

X

X

X

X

X

X

X

X

X

–

X

–

–

–

–

–

–

–

–

X

–

X

–

–

–

–

–

–

–

–

–

–

–

–

–

X

–

–

X

X

X

X

–

–

–

–

–

–

X

X

X

X

–

–

–

–

–

–