Functional Peripherals Registers
143
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
Cortex-M4F Peripherals
2.4.5.6
CCR Register (Offset = D14h) [reset = 00000200h]
CCR is shown in
and described in
Configuration Control Register. Use the Configuration Control Register to: enable NMI, HardFault and
FAULTMASK to ignore bus fault, trap divide by zero and unaligned accesses, enable user access to the
Software Trigger Exception Register, control entry to Thread Mode.
Figure 2-56. CCR Register
31
30
29
28
27
26
25
24
RESERVED
R/W-0h
23
22
21
20
19
18
17
16
RESERVED
R/W-0h
15
14
13
12
11
10
9
8
RESERVED
STKALIGN
BFHFNMIGN
R/W-0h
R/W-1h
R/W-0h
7
6
5
4
3
2
1
0
RESERVED
DIV_0_TRP
UNALIGN_TRP
RESERVED
USERSETMPE
ND
NONBASETHR
EDENA
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
Table 2-64. CCR Register Field Descriptions
Bit
Field
Type
Reset
Description
31-10
RESERVED
R/W
0h
9
STKALIGN
R/W
1h
Stack alignment bit.
0b (R/W) = Only 4-byte alignment is ensured for the SP used prior to
the exception on exception entry.
1b (R/W) = On exception entry, the SP used prior to the exception is
adjusted to be 8-byte aligned and the context to restore it is saved.
The SP is restored on the associated exception return.
8
BFHFNMIGN
R/W
0h
When enabled, this causes handlers running at priority -1 and -2
(Hard Fault, NMI, and FAULTMASK escalated handlers) to ignore
Data Bus faults caused by load and store instructions. When
disabled, these bus faults cause a lock-up. You must only use this
enable with extreme caution. All data bus faults are ignored therefore
you must only use it when the handler and its data are in absolutely
safe memory. Its normal use is to probe system devices and bridges
to detect control path problems and fix them.
7-5
RESERVED
R/W
0h
4
DIV_0_TRP
R/W
0h
Trap on Divide by 0. This enables faulting/halting when an attempt is
made to divide by 0. The relevant Usage Fault Status Register bit is
DIVBYZERO.
3
UNALIGN_TRP
R/W
0h
Trap for unaligned access. This enables faulting/halting on any
unaligned half or full word access. Unaligned load-store multiples
always fault. The relevant Usage Fault Status Register bit is
UNALIGNED.
2
RESERVED
R/W
0h
1
USERSETMPEND
R/W
0h
If written as 1, enables user code to write the Software Trigger
Interrupt register to trigger (pend) a Main exception, which is one
associated with the Main stack pointer.
0
NONBASETHREDENA
R/W
0h
When 0, default, It is only possible to enter Thread mode when
returning from the last exception. When set to 1, Thread mode can
be entered from any level in Handler mode by controlled return
value.