System Control Block (SCB) Register Descriptions
1671
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
Cortex-M3 Peripherals
25.6.5 Application Interrupt and Reset Control (APINT) Register, offset 0xD0C
The Application Interrupt and Reset Control (APINT) 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, 0x05FA must be written to the VECTKEY field, otherwise the write is ignored.
The PRIGROUP field indicates the position of the binary point that splits the INTx fields in the Interrupt
Priority (PRIx) registers into separate group priority and subpriority fields.
shows how the
PRIGROUP value controls this split. The bit numbers in the Group Priority Field and Subpriority Field
columns in the table refer to the bits in the INTA field. For the INTB field, the corresponding bits are 15:13;
for INTC, 23:21; and for INTD, 31:29.
Note:
This register can only be accessed from privileged mode.
Note:
Determining preemption of an exception uses only the group priority field.
(1)
INTx field showing the binary point. An x denotes a group priority field bit, and a y denotes a subpriority field bit.
Table 25-42. Interrupt Priority Levels
PRIGROUP Bit
Field
Binary Point
(1)
Group Priority
Field
Subpriority Field
Group Priorities
Subpriorities
0x0 - 0x4
bxxx.
[7:5]
None
8
1
0x5
bxx.y
[7:6]
[5]
4
2
0x6
bx.yy
[7]
[6:5]
2
4
0x7
b.yyy
None
[7:5]
1
8
Figure 25-36. Application Interrupt and Reset Control (APINT) Register
31
16
VECTKEY
R/W-FA05h
15
14
11
10
8
7
3
2
1
0
ENDIANESS
Reserved
PRIGROUP
Reserved
SYSRESREQ
VECTCLRACT
VECTRESET
R-0
R-0
R/W-0
R-0
W-0
W-0
W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 25-43. Application Interrupt and Reset Control (APINT) Register Field Descriptions
Bit
Field
Value
Description
31-16
VECTKEY
Register Key
This field is used to guard against accidental writes to this register. 0x05FA must be written to this
field in order to change the bits in this register.
On a read, 0xFA05 is returned.
15
ENDIANESS
Data Endianess
This implementation uses only little-endian mode so this is cleared to 0.
14-11
Reserved
Reserved
10-8
PRIGROUP
Interrupt Priority Grouping
This field determines the split of group priority from subpriority (see
for more
information).
7-3
Reserved
Reserved
2
SYSRESREQ
System Reset Request
0
No effect
1
Resets the core and all on-chip peripherals except the Debug interface.
This bit is automatically cleared during the reset of the core and reads as 0.
1
VECTCLRACT
Clear Active NMI / Fault
This bit is reserved for Debug use and reads as 0. This bit must be written as a 0, otherwise
behavior is unpredictable.