at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 155

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

19. AT91SAM9263 Bus Matrix
19.1
19.2
19.3
19.3.1
19.3.2
19.3.3
6249D–ATARM–20-Dec-07
Description
Memory Mapping
Special Bus Granting Techniques
No Default Master
Last Access Master
Fixed Default Master
Bus Matrix implements a multi-layer AHB, based on AHB-Lite protocol, that enables parallel
access paths between multiple AHB masters and slaves in a system, which increases the over-
all bandwidth. Bus Matrix interconnects 9 AHB Masters to 8 AHB Slaves. The normal latency to
connect a master to a slave is one cycle except for the default master of the accessed slave
which is connected directly (zero cycle latency).
The Bus Matrix user interface is compliant with ARM Advanced Peripheral Bus and provides a
Chip Configuration User Interface with Registers that allow the Bus Matrix to support application
specific features.
Bus Matrix provides one decoder for every AHB Master Interface. The decoder offers each AHB
Master several memory mappings. In fact, depending on the product, 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 Master Remap Control Register (MATRIX_MRCR) that
allows to perform remap action for every master independently.
The Bus Matrix provides some speculative bus granting techniques in order to anticipate access
requests from some masters. This mechanism allows to reduce latency at first accesses of a
burst or single transfer. The bus granting mechanism allows to set 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 and fixed default master.
At the end of the current access, if no other request is pending, the slave is disconnected from
all masters. No Default Master, suits low power mode.
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.
At the end of the current access, if no other request is pending, the slave connects to itsfixed
default master. Unlike last access master, the fixed master doesn’t change unless the user mod-
ifies it by a software action (field FIXED_DEFMSTR of the related MATRIX_SCFG).
To change from one kind of default master to another, the Bus Matrix user interface provides the
Slave Configuration Registers, one for each slave, that allow to 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 allows to choose
the default master type (no default, last access master, fixed default master) whereas the 4-bit
AT91SAM9263 Preliminary
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