Cortex-A8 R2P2.pdf - ARM Information Center

Programmer’s ModelThumbEE Configuration RegisterThe purpose of the ThumbEE Configuration Register is to control access to theThumbEE HandlerBase Register.The ThumbEE Configuration Register is:• in CP14 register c0• a 32-bit register, with access rights that depend on the current privilege:— the result of an unprivileged write to the register is Undefined— unprivileged reads, and privileged reads and writes, are permitted.Figure 2-2 shows the bit arrangement of the ThumbEE Configuration Register.31 1 0ReservedXEDBitsFieldFunctionFigure 2-2 ThumbEE Configuration Register formatTable 2-1 shows how the bit values correspond with the ThumbEE ConfigurationRegister.Table 2-1 ThumbEE Configuration Register bit functions[31:1] - Reserved. Unpredictable (UNP), Should-Be-Zero (SBZ).[0] XED eXecution Environment Disable bit. Controls unprivileged access to the ThumbEE HandlerBaseRegister:0 = Unprivileged access permitted. See Access to ThumbEE registers on page 2-9 for details.1 = Unprivileged access disabled.The reset value of this bit is 0.Any change to this register is only guaranteed to be visible to subsequent instructionsafter the execution of an ISB instruction. However, a read of this register always returnsthe last value written to the register.To access the ThumbEE Configuration Register, read or write CP14 with:MRC p14, 6, , c0, c0, 0 ; Read ThumbEE Configuration RegisterMCR p14, 6, , c0, c0, 0 ; Write ThumbEE Configuration RegisterARM DDI 0344E Copyright © 2006-2008 ARM Limited. All rights reserved. 2-7