AT91SAM9XE128_1 Datasheet, PDF (167/866 Pages) ATMEL Corporation – AT91 ARM Thumb Microcontrollers

AT91SAM9XE128/256/512 Preliminary
21.5.2 Bus Matrix Slave Configuration Registers
Register Name:MATRIX_SCFG0...MATRIX_SCFG4
Address: 0xFFFFEE40
Access Type: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 slave by when very long burst are used.
This limit should not be very small though. Unreasonable small value will break every burst and Bus Matrix will spend its
time to arbitrate without performing any data transfer. 16 cycles is a reasonable value for SLOT_CYCLE.
• DEFMASTR_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 acccess 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 stay connected with 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 which
number 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 DEFMASTR_TYPE is 2. Specifying the number of a
master which is not connected to the selected slave is equivalent to setting DEFMASTR_TYPE to 0.
• ARBT : Arbitration Type
0: Round-Robin Arbitration
1: Fixed Priority Arbitration
2: Reserved
3: Reserved
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