SAM3S_14 Datasheet, PDF (345/1087 Pages) ATMEL Corporation – AT91SAM ARM-based Flash MCU

23.8.2 Bus Matrix Slave Configuration Registers
Name:
MATRIX_SCFG0..MATRIX_SCFG4
Access: Read-write
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
–
–
–
–
–
–
–
–
7
6
5
4
3
2
1
0
SLOT_CYCLE
• 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 though. An unreasonable 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
0: No Default Master
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 Default Master
At the end of current slave access, if no other master request is pending, the slave stays connected to the last master hav-
ing accessed it.
This results in not having the one cycle latency when the last master re-tries access on the slave again.
2: Fixed Default Master
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 re-tries access on the slave again.
• 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 mas-
ter which is not connected to the selected slave is equivalent to setting DEFMSTR_TYPE to 0.
• ARBT: Arbitration Type
0: Round-Robin Arbitration
1: Fixed Priority Arbitration
2: Reserved
3: Reserved
SAM3S [DATASHEET]
6500E–ATARM–11-Feb-13
345