Cortex-A8 R2P2.pdf - ARM Information Center

System Control Coprocessor3.2.72 c13, Context ID RegisterThe purpose of the Context ID Register is to provide information on the current ASIDand process ID, for example for the ETM and debug logic.Debug logic uses the ASID information to enable process-dependent breakpoints andwatchpoints. The ASID field of the Context ID Register and FCSE PID Register cannotbe used simultaneously. The FCSE PID Register remapping of VA to MVA has priorityover setting the ASID field to designate non-global pages. Therefore, non-global pagescannot be used if the FCSE PID Register is set to a non-zero value.The Context ID Register is:• a read/write register banked for Secure and Nonsecure states• accessible in privileged modes only.Figure 3-66 shows the bit arrangement of the Context ID Register.31 8 7 0PROCIDASIDBits Field FunctionFigure 3-66 Context ID Register formatTable 3-144 shows how the bit values correspond with the Context ID Registerfunctions.Table 3-144 Context ID Register bit functions[31:8] PROCID Extends the ASID to form the process ID and identifies the current process. The reset value is 0.[7:0] ASID Holds the ASID of the current process to identify the current ASID. The reset value is 0.Table 3-145 shows the results of attempted access for each mode.Table 3-145 Results of access to the Context ID Register aSecure privileged Nonsecure privileged Secure User Nonsecure UserRead Write Read Write Read Write Read WriteSecuredataSecuredataNonsecuredataNonsecuredataUndefined Undefined Undefined UndefinedARM DDI 0344E Copyright © 2006-2008 ARM Limited. All rights reserved. 3-161