SAM3S8B Atmel Corporation, SAM3S8B Datasheet - Page 365

• Manufacturer Part Number: SAM3S8B
• Manufacturer: Atmel Corporation

22.5.3
22.6
22.7
11090A–ATARM–10-Feb-12
11090A–ATARM–10-Feb-12
System I/O Configuration
Write Protect Registers
Fixed Priority Arbitration
ter will not cause any latency whereas other non privileged masters will still get one latency
cycle. This technique can be used for masters that mainly perform single accesses.
This algorithm allows the Bus Matrix arbiters to dispatch the requests from different masters to
the same slave by using the fixed priority defined by the user. If two or more master’s requests
are active at the same time, the master with the highest priority number is serviced first. If two or
more master’s requests with the same priority are active at the same time, the master with the
highest number is serviced first.
For each slave, the priority of each master may be defined through the Priority Registers for
Slaves (MATRIX_PRAS and MATRIX_PRBS).
The System I/O Configuration register (CCFG_SYSIO) allows to configure some I/O lines in
System I/O mode (such as JTAG, ERASE, USB, etc...) or as general purpose I/O lines. Enabling
or disabling the corresponding I/O lines in peripheral mode or in PIO mode (PIO_PER or
PIO_PDR registers) in the PIO controller as no effect. However, the direction (input or output),
pull-up, pull-down and other mode control is still managed by the PIO controller.
To prevent any single software error that may corrupt MATRIX behavior, the entire MATRIX
address space from address offset 0x000 to 0x1FC can be write-protected by setting the WPEN
bit in the MATRIX Write Protect Mode Register (MATRIX_WPMR).
If a write access to anywhere in the MATRIX address space from address offset 0x000 to 0x1FC
is detected, then the WPVS flag in the MATRIX Write Protect Status Register (MATRIX_WPSR)
is set and the field WPVSRC indicates in which register the write access has been attempted.
The WPVS flag is reset by writing the MATRIX Write Protect Mode Register (MATRIX_WPMR)
with the appropriate access key WPKEY.
SAM3S8/SD8
SAM3S8/SD8
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