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SAM G51 [DATASHEET]
11209C–ATARM–20-Dec-13
20.3.2 Matrix Slaves
The Bus Matrix manages four slaves. Each slave has its own arbiter, providing a different arbitration per slave.
20.3.3 Master to Slave Access
Table 20-3 gives valid paths for master to slave access. The paths shown as “-” are forbidden or not wired, e.g. access
from the processor I/D bus to internal SRAM..
20.4
Memory Mapping
The Bus Matrix provides one decoder for every AHB master interface. The decoder offers each AHB master several
memory mappings. Depending on the product, each memory area may be assigned to several slaves. Thus it is possible
to boot at the same address while using different AHB slaves.
20.5
Special Bus Granting Techniques
The Bus Matrix provides some speculative bus granting techniques in order to anticipate access requests from some
masters, reducing latency at the first access of a burst or single transfer. The bus granting technique sets a 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
20.5.1 No Default Master
At the end of the current access, if no other request is pending, the slave is disconnected from all masters. This is
suitable when the device is in low-power mode.
20.5.2 Last Access Master
At the end of the current access, if no other request is pending, the slave remains connected to the last master that
performed an access request.
Table 20-2.
List of Bus Matrix Slaves
Slave 0
Internal SRAM
Slave 1
Internal ROM
Slave 2
Internal Flash
Slave 3
Peripheral Bridge
Table 20-3.
Master to Slave Access
Masters
0
1
2
Slaves
Processor
I/D Bus
Processor
S Bus
PDC
0
Internal SRAM
–
X
1
Internal ROM
X
–
X
2
Internal Flash
X
–
3
Peripheral Bridge
–
X