• Locked Locked
  • Replies 5 replies
  • Subscribers 119 subscribers
  • Views 3481 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Thumb mode, Thumb2 MRS insturction issue.

Kim DonaSam
Note: This was originally posted on 28th July 2011 at http://forums.arm.com

Dear All

I have find a strange behavior on cortexA9/R4,

My mode data code as below 

0x0   0x8100F3EF    MRS R1,CPSR                 (current CPSR value is 0x1F3)

However when I execute the line,  the value in R1 is 0x1D3,   Isn't it should be 0x1F3?

Is it a chip bug? or there is some other reason?

If anyone knows the answer, please let me know.
Parents
  • Note: This was originally posted on 29th July 2011 at http://forums.arm.com


    Bit 5 is the T bit (ARM or Thumb state).  The value you're getting back implies you are in fact in ARM state.  How do you know what the value should be?  Are you using a debugger?



    I'm using a debugger

    data in 0x0700000C is MRS r1,cpsr[0x8100F3EF] , start program at 0x07000002 [thumb mode] and stop at Bp 0x0700001A, but the R1 value is not 0x1F3, it shown as 0x1D3



Reply
  • Note: This was originally posted on 29th July 2011 at http://forums.arm.com


    Bit 5 is the T bit (ARM or Thumb state).  The value you're getting back implies you are in fact in ARM state.  How do you know what the value should be?  Are you using a debugger?



    I'm using a debugger

    data in 0x0700000C is MRS r1,cpsr[0x8100F3EF] , start program at 0x07000002 [thumb mode] and stop at Bp 0x0700001A, but the R1 value is not 0x1F3, it shown as 0x1D3



Children
No data