PM0214 datasheet(222/245 Pages) STMICROELECTRONICS

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Core peripherals

PM0214

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DocID022708 Rev 4

4.4.11

Usage fault status register (UFSR)

Bits 31:26

Reserved, must be kept cleared

Bit 25

DIVBYZERO: Divide by zero usage fault. When the processor sets this bit to 1, the PC value

stacked for the exception return points to the instruction that performed the divide by zero.

Enable trapping of divide by zero by setting the DIV_0_TRP bit in the CCR to 1, see

Configuration and control register (CCR) on page 215.

0: No divide by zero fault, or divide by zero trapping not enabled

1: The processor has executed an SDIV or UDIV instruction with a divisor of 0.

Bit 24

UNALIGNED: Unaligned access usage fault. Enable trapping of unaligned accesses by

setting the UNALIGN_TRP bit in the CCR to 1, see Configuration and control register (CCR)

on page 215.

Unaligned LDM, STM, LDRD, and STRD instructions always fault irrespective of the setting of

UNALIGN_TRP.

0: No unaligned access fault, or unaligned access trapping not enabled

1: the processor has made an unaligned memory access.

Bits 23:20

Reserved, must be kept cleared

Bit 19

NOCP: No coprocessor usage fault. The processor does not support coprocessor instructions:

0: No usage fault caused by attempting to access a coprocessor

1: the processor has attempted to access a coprocessor.

Bit 18

INVPC: Invalid PC load usage fault, caused by an invalid PC load by EXC_RETURN:

When this bit is set to 1, the PC value stacked for the exception return points to the instruction

that tried to perform the illegal load of the PC.

0: No invalid PC load usage fault

1: The processor has attempted an illegal load of EXC_RETURN to the PC, as a result of an

invalid context, or an invalid EXC_RETURN value.

Bit 17

INVSTATE: Invalid state usage fault. When this bit is set to 1, the PC value stacked for the

exception return points to the instruction that attempted the illegal use of the EPSR.

This bit is not set to 1 if an undefined instruction uses the EPSR.

0: No invalid state usage fault

1: The processor has attempted to execute an instruction that makes illegal use of the

EPSR.

Bit 16

UNDEFINSTR: Undefined instruction usage fault. When this bit is set to 1, the PC value

stacked for the exception return points to the undefined instruction.

An undefined instruction is an instruction that the processor cannot decode.

0: No undefined instruction usage fault

1: The processor has attempted to execute an undefined instruction.

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