J-Link / J-Trace User Guide (UM08001) - Microcontrollers

210 CHAPTER 11 Support and FAQs
A: J-Link / J-Trace handles cache cleaning directly through JTAG commands. Unlike
other emulators, it does not have to download code to the target system. This
makes setting up J-Link / J-Trace easier. Therefore, a cache clean area is not
required.
Registers on ARM 7 / ARM 9 targets
Q: I’m running J-Link.exe in parallel to my debugger, on an ARM 7 target. I can read
memory okay, but the processor registers are different. Is this normal?
A: If memory on an ARM 7/9 target is read or written the processor registers are
modified. When memory read or write operations are performed, J-Link preserves
the register values before they are modified. The register values shown in the
debugger’s register window are the preserved ones. If now a second instance, in
this case J-Link.exe, reads the processor registers, it reads the values from the
hardware, which are the modified ones. This is why it shows different register values.
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