Programming Model
1577
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
Cortex-M3 Processor
24.4.4.7 Fault Mask Register (FAULTMASK)
The FAULTMASK register prevents activation of all exceptions except for the Non-Maskable Interrupt
(NMI). Exceptions should be disabled when they might impact the timing of critical tasks. This register is
only accessible in privileged mode. The MSR and MRS instructions are used to access the FAULTMASK
register, and the CPS instruction may be used to change the value of the FAULTMASK register. See the
Cortex-M3 Instruction Set Technical User's Manual
for more information on these instructions. For more
information on exception priority levels, see .
Figure 24-9. Fault Mask Register (FAULTMASK)
31
1
0
Reserved
FAULTMASK
R-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 24-10. Fault Mask Register (FAULTMASK) Field Descriptions
Bit
Field
Value
Description
31-1
Reserved
Reserved
0
FAULTMASK
Priority mask
0
No effect
1
Prevents the activation of all exceptions except for NMI.
24.4.4.8 Base Priority Mask Register (BASEPRI)
The BASEPRI register defines the minimum priority for exception processing. When BASEPRI is set to a
nonzero value, it prevents the activation of all exceptions with the same or lower priority level as the
BASEPRI value. Exceptions should be disabled when they might impact the timing of critical tasks. This
register is only accessible in privileged mode. For more information on exception priority levels, see
.
Figure 24-10. Base Priority Mask Register (BASEPRI)
31
8
7
5
4
0
Reserved
BASEPRI
Reserved
R-0
R/W-0
R-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 24-11. Base Priority Mask Register Field Descriptions
Bit
Field
Value
Description
31-1
Reserved
Reserved
7-5
BASEPRI
Base priority
Any exception that has a programmable priority level with the same or lower priority as the value of
this field is masked. The PRIMASK register can be used to mask all exceptions with programmable
priority levels. Higher priority exceptions have lower priority levels.
0h
All exceptions are unmasked.
1h
All exceptions with priority level 1-7 are masked
2h
All exceptions with priority level 2-7 are masked
3h
All exceptions with priority level 3-7 are masked.
4h
All exceptions with priority level 4-7 are masked.
5h
All exceptions with priority level 5-7 are masked.
6h
All exceptions with priority level 6-7 are masked
7h
All exceptions with priority level 7 are masked.
4-0
Reserved
Software should not rely on the value of a reserved bit. To provide compatibility with future
products, the value of a reserved bit should be preserved across a read-modify-write operation.