Atmel SAM4S Series, Preliminary Data Sheet

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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
11.9.1.5 Application Interrupt and Reset Control Register
Name: SCB_AIRCR
Access: Read-write
Reset:
0x000000000
The SCB_AIRCR register provides priority grouping control for the exception model, endian status for data accesses, and
reset control of the system. To write to this register, write 0x5FA to the VECTKEY field, otherwise the processor ignores the
write.
• VECTKEYSTAT: Register Key
Read:
Reads as 0xFA05.
• VECTKEY: Register Key
Write:
Writes 0x5FA to VECTKEY, otherwise the write is ignored.
• ENDIANNESS: Data Endianness
0: Little-endian.
1: Big-endian.
• PRIGROUP: Interrupt Priority Grouping
This field determines the split of group priority from subpriority. It shows the position of the binary point that splits the PRI_n
fields in the Interrupt Priority Registers into separate group priority and subpriority fields. The table below shows how the
PRIGROUP value controls this split:
31 30 29 28 27 26 25 24
VECTKEYSTAT/VECTKEY
23 22 21 20 19 18 17 16
VECTKEYSTAT/VECTKEY
15 14 13 12 11 10 9 8
ENDIANNESS – PRIGROUP
7 6 5 4 3 2 1 0
– SYSRESETREQ
VECTCLRACTI
VE
VECTRESET
Interrupt Priority Level Value, PRI_N[7:0] Number of
PRIGROUP Binary Point
(1)
Group Priority bits Subpriority bits Group Priorities Subpriorities
0b000 bxxxxxxx.y [7:1] None 128 2
0b001 bxxxxxx.yy [7:2] [4:0] 64 4
0b010 bxxxxx.yyy [7:3] [4:0] 32 8
0b011 bxxxx.yyyy [7:4] [4:0] 16 16
0b100 bxxx.yyyyy [7:5] [4:0] 8 32