Table 9. Basepri Register Bit Assignments; Table 10. Control Register Bit Definitions; Figure 7. Basepri Bit Assignments - ST STM32F4 Series Programming Manual

The Cortex-M4 processor
Base priority mask register
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 same or
lower priority level as the BASEPRI value. See the register summary in
for its attributes.
31
Bits
Bits 31:8
Bits 7:4
Bits 3:0
1. This field is similar to the priority fields in the interrupt priority registers. See
(NVIC_IPRx) on page 214
lower exception priorities.
CONTROL register
The CONTROL register controls the stack used and the privilege level for software
execution when the processor is in Thread mode and indicates whether the FPU state is
active. See the register summary in
Bits
Bits 31:3
Bit 2
Bit 1
Bit 0
24/260
Figure 7 shows the bit assignments.

Figure 7. BASEPRI bit assignments

Reserved

Table 9. BASEPRI register bit assignments

Function
Reserved
BASEPRI[7:4] Priority mask bits
0x00: no effect
Nonzero: defines the base priority for exception processing.
The processor does not process any exception with a priority value greater than or
equal to BASEPRI.
Reserved
for more information. Remember that higher priority field values correspond to

Table 10. CONTROL register bit definitions

Function
Reserved
FPCA: Indicates whether floating-point context currently active:
0: No floating-point context active
1: Floating-point context active.
The Cortex-M4 uses this bit to determine whether to preserve floating-point state
when processing an exception.
SPSEL: Active stack pointer selection. Selects the current stack:
0: MSP is the current stack pointer
1: PSP is the current stack pointer.
In Handler mode this bit reads as zero and ignores writes. The Cortex-M4 updates
this bit automatically on exception return.
nPRIV: Thread mode privilege level. Defines the Thread mode privilege level.
0: Privileged
1: Unprivileged.
DocID022708 Rev 6
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Table 2 on page 17 for its attributes.
PM0214
Table 2 on page 17
8 7 0
BASEPRI
Interrupt priority registers