Add explanatory note about C_DEBUGEN
@@ -34,8 +34,14 @@ impl DCB {
// unset bit 24 / TRCENA
unsafe { self.demcr.modify(|w| w & !DCB_DEMCR_TRCENA); }
- /// Is there a debugger attached?
- pub fn is_debugger_attached(&self) -> bool {
- self.dhcsr.read() & 0x1 == 1
+ /// Is there a debugger attached? (see note)
+ ///
+ /// N.B. This function is [reported not to
+ /// work](http://web.archive.org/web/20180821191012/https://community.nxp.com/thread/424925#comment-782843)
+ /// on Cortex-M0 devices. Per the ARM v6-M Architecture Reference Manual, "Access to the DHCSR
+ /// from software running on the processor is IMPLEMENTATION DEFINED". Indeed, from the
+ /// [Cortex-M0+ r0p1 Technical Reference Manual](http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0484c/BABJHEIG.html), "Note Software cannot access the debug registers."
+ pub fn is_debugger_attached() -> bool {
+ unsafe { (*Self::ptr()).dhcsr.read() & 0x1 == 1 }
}
}
