Cortex-M3 Processor (Reference Material)
UG0331 User Guide Revision 15.0
106
The bit assignments are:
Figure 34 •
AIRCR Bit Assignments
3.7.2.5.1
Binary Point
The PRIGROUP field indicates 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 following table shows how the
PRIGROUP value controls this split. <If you implement fewer than 8 priority bits you might require more
explanation here, and want to remove invalid rows from the table, and modify the entries in the
number of
columns.>
Table 55 •
AIRCR Bit Assignments
Bits
Name
Type
Function
[31:16]
Write:
VECTKEYSTAT
Read: VECTKEY
RW
Register key:
Reads as 0xFA05.
On writes, write 0x05FA to VECTKEY, otherwise the write is ignored.
[15]
ENDIANNESS
RO
Data endianness bit:
0: Little-endian
1: Big-endian.
ENDIANNESS is set from the
BIGEND
configuration signal during reset.
[14:11]
Reserved
[10:8]
PRIGROUP
R/W
Interrupt priority grouping field. This field determines the split of group
priority from subpriority, see
"Binary Point" on page 102
.
[7:3]
Reserved.
[2]
SYSRESETREQ
WO
System reset request:
0: no system reset request
1: asserts a signal to the outer system that requests a reset.
This is intended to force a large system reset of all major components
except for debug.
This bit reads as 0.
[1]
VECTCLRACTIVE
WO
Reserved for Debug use. This bit reads as 0. When writing to the register
you must write 0 to this bit, otherwise behavior is Unpredictable.
[0]
VECTRESET
WO
Reserved for Debug use. This bit reads as 0. When writing to the register
you must write 0 to this bit, otherwise behavior is Unpredictable.
Table 56 •
Priority Grouping
PRIGROUP
Interrupt priority level value, PRI_
N
[7:0]
Number of
Binary point
1
Group priority bits
Subpriority bits
Group priorities
Subpriorities
b000
bxxxxxxx.y
[7:1]
[0]
128
2
On read: VECTKEYSTAT
On write: VECTKEY
31
16 15 14
11 10
8 7
3 2 1 0
Reserved
Reserved
ENDIANNESS
PRIGROUP
SYSRESETREQ
VECTCLRACTIVE
VECTRESET
Reserved for Debug use