Rainbow Electronics AT91CAP9S250A - Manual (Page 136)

136
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
20.5.2 Bus Matrix Slave Configuration Registers
Register Name: MATRIX_SCFG0...MATRIX_SCFG9
Access Type: Read/Write
• SLOT_CYCLE: Maximum Number of Allowed Cycles for a Burst
When the SLOT_CYCLE limit is reached for a burst, it may be broken by another master trying to access this slave.
This limit has been placed to avoid locking a very slow slave when very long bursts are used.
Note that an unreasonably small value breaks every burst and the Bus Matrix then arbitrates 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 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 remains connected to the last master
that accessed it.
This results in not having the one cycle latency when the last master tries access to 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 of which has been written in the FIXED_DEFMSTR field.
This results in not having the one cycle latency when the fixed master tries access to 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
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