ST STM8 User Manual

Debug module (DM) UM0470
24/39 DocID14024 Rev 4
4.5 Software breakpoint mode
The software breakpoint mode is reserved for the debugging tools to insert breakpoints into
the user code by substituting a user instruction with a software break (reserved BKPT
instruction #8b).
The software breakpoint mode
is enabled using the SWBKPE bit in the DM control/status
register 2 (DM_CSR2) (see Section 4.12.10 on page 33).
When a BKPT instruction is decoded, the CPU is
stalled and the STALL and SWBKF bits
are set by hardware to indicate that a software breakpoint has occurred. To resume the
execution, the debugger must restore the user's instruction, then set the FLUSH bit and
clear the STALL bit.
4.6 Timing description
This paragraph defines when the debug module stalls the CPU when using the different
breakpoint sources.
• T
he STM8 MCU instruction can be modeled in time with an op-code/operand with a
FETCH, DECODE and EXECUTION phases as shown in Figure 12.
The timing information is
based on these models.
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Figure 12. STM8 MCU instruction model
4.7 Abort
The stall is generated immediately when writing the STALL bit in the DM_CSR2 register.
Figure 13. STM8 Debug module stall timing
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ST STM8 Specifications

General

Brand	ST
Model	STM8
Category	Control Unit
Language	English