Programming Model
1576
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
Cortex-M3 Processor
Table 24-8. Program Status Register (PSR) Field Descriptions (continued)
Bit
Field
Value
Description
6-0
ISRNUM
IPSR ISR Number. This field contains the exception type number of the current Interrupt Service
Routine (ISR).
0h
Thread mode
1h
Reserved
2h
NMI
3h
Hard fault
4h
Memory management fault
5h
Bus fault
6h
Usage fault
0x07h-
0x0Ah
Reserved
Bh
SVCall
Ch
Reserved for Debug
Dh
Reserved
Eh
PendSV
Fh
SysTick
10h
Interrupt Vector 0
11h
Interrupt Vector 1
...
...
6Ah
Interrupt Vector 90
0x6B-
0x7F
Reserved
See
for more information. The value of this field is only meaningful when accessing
PSR or IPSR.
24.4.4.6 Priority Mask Register (PRIMASK)
The PRIMASK register prevents activation of all exceptions with programmable priority. Reset, non-
maskable interrupt (NMI), and hard fault are the only exceptions with fixed priority. 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 PRIMASK register, and the CPS instruction
may be used to change the value of the PRIMASK 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 24-8. Priority Mask Register (PRIMASK)
31
1
0
Reserved
PRIMASK
R-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 24-9. Priority Mask Register (PRIMASK) Field Descriptions
Bit
Field
Value
Description
31-1
Reserved
Reserved
0
PRIMASK
Priority mask
0
No effect
1
Prevents the activation of all exceptions with configurable priority.