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ARM DDI 0363E Copyright © 2009 ARM Limited. All rights reserved. 11-64
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}
Reading the PC in debug state
Example 11-15 shows the code to read the PC.
Example 11-15 Reading the PC
ReadPC()
{
// Step 1. Save R0
saved_r0 := ReadRegister(0);
// Step 2. Execute the instruction MOV r0, pc through the ITR.
ExecuteARMInstruction(0xE1A0000F);
// Step 3. Read the value of R0 that now contains the PC.
pc := ReadRegister(0);
// Step 4. Restore the value of R0.
WriteRegister(0, saved_r0);
return pc;
}
Note
You can use a similar sequence to write to the PC to set the return address when leaving debug
state.
Reading the CPSR in debug state
Example 11-16 shows the code for reading the CPSR.
Example 11-16 Reading the CPSR
ReadCPSR()
{
// Step 1. Save R0.
saved_r0 := ReadRegister(0);
// Step 2. Execute instruction MRS R0, CPSR through the ITR.
ExecuteARMInstruction(0xE10F0000);
// Step 3. Read the value of R0 that now contains the CPSR
cpsr_val := ReadRegister(0);
// Step 4. Restore the value of R0.
WriteRegister(0, saved_r0);
return cpsr_val;
}
Note
You can use similar sequences to read the SPSR in Privileged modes.
Writing the CPSR in debug state
Example 11-17 on page 11-65 shows the code for writing the CPSR.