Datasheet

424
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
25.8.2 Bus Matrix Slave Configuration Registers
Name: MATRIX_SCFG0..MATRIX_SCFG4
Address: 0x400E0240
Access: Read/Write
• SLOT_CYCLE: Maximum Number of Allowed Cycles for a Burst
When the SLOT_CYCLE limit is reach for a burst, it may be broken by another master trying to access this slave.
This limit has been placed to avoid locking very slow slaves when very long bursts are used.
This limit should not be very small. An unreasonably small value will break every burst and the Bus Matrix will spend its time to
arbitrate without performing any data transfer. 16 cycles is a reasonable value for SLOT_CYCLE.
• DEFMSTR_TYPE: Default Master Type
• FIXED_DEFMSTR: Fixed Default Master
This is the number of the default master for this slave. Only used if DEFMSTR_TYPE is 2. Specifying the number of a master
which is not connected to the selected slave is equivalent to setting DEFMSTR_TYPE to 0.
• ARBT: Arbitration Type
31 30 29 28 27 26 25 24
–––––– ARBT
23 22 21 20 19 18 17 16
– – – FIXED_DEFMSTR DEFMSTR_TYPE
15 14 13 12 11 10 9 8
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76543210
SLOT_CYCLE
Value Name Description
0 NO_DEFAULT
At the end of current slave access, if no other master request is pending, the slave is
disconnected from all masters.
This results in having a one cycle latency for the first access of a burst transfer or for a
single access.
1 LAST
At the end of current slave access, if no other master request is pending, the slave
stays connected to the last master having accessed it.
This results in not having the one cycle latency when the last master tries to access the
slave again.
2 FIXED
At the end of the current slave access, if no other master request is pending, the slave
connects to the fixed master the number that has been written in the
FIXED_DEFMSTR field.
This results in not having the one cycle latency when the fixed master tries to access
the slave again.
Value Name Description
0 ROUND_ROBIN Round-robin arbitration
1 FIXED_PRIORITY Fixed priority arbitration