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Floating-point Exception Register

The FPEXC Register characteristics are:

Purpose
Provides global enable control of the VFP extension.
Usage constraints

This register is:

  • Only accessible in the Non-secure state if the CP10 and CP11 bits in the NSACR are set to 1. See  VFP register access.
  • Only accessible in privileged modes, and only if access to coprocessors CP10 and CP11 is enabled in the CPACR. See  VFP register access.
Configurations

Available in all configurations.

Attributes
See  Register summary.

The following figure shows the FPEXC Register bit assignments.

Figure 2-5 FPEXC Register bit assignments


The following table shows the FPEXC Register bit assignments.

Table 2-8 FPEXC Register bit assignments

Bits

Name

Function

[31]

EX The Cortex®â€‘A5 FPU does not generate asynchronous VFP exceptions, therefore this bit is RAZ/WI.

[30]

EN

FPU enable bit:

b0 = FPU disabled.

b1 = FPU enabled.

The EN bit is cleared to 0 at reset.

[29] DEX

Defined synchronous instruction exceptional flag. The Cortex‑A5 FPU sets this bit when generating a synchronous bounce because of an attempt to execute a vector operation. All other UNDEFINED Instruction exceptions clear this bit to zero.

See the ARM Architecture Reference Manual, ARMv7-A and ARMv7-R edition for more information.

[28:0] Reserved RAZ/WI.

You can access the FPEXC Register with the following VMSR instructions:

VMRS <Rd>, FPEXC ; Read Floating-Point Status and Control Register
VMSR FPEXC, <Rt> ; Write Floating-Point Status and Control Register
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