Architecture
87
n DSS (bit 0)
Set to 1 to indicate a Single Step exception.
DBp and DSS bits indicate the most recent debug exception. Each bit represents one of the
two debug exceptions and is set to 1 accordingly when that exception occurs.
Note : DSS has a higher priority than DBp, since they occur in the pipeline E stage. For
this reason DSS and DBp are not raised at the same time.
n 0
Ignored when written; returns 0 when read.
n <R>
Reserved. Undefined value.
8.2 Debug Exceptions(1) Types of debug exceptions
There are two debug exceptions, as follows.
1) Debug Single Step (DSS)
When the Debug register SS bit is set, this exception is raised each time an instruction is
executed.
2) Debug Breakpoint (DBp)
This exception is raised when an SDBBP instruction is executed.
Note : Since the real-time debugging system function has priority, the above two functions are
disabled when the real-time debugging system is used.