Datasheet

Breakpoint (BKP) Module
Breakpoint Types
MC9S12DP256 — Revision 1.1
Breakpoint (BKP) Module
Breakpoint Types
The priority of the breakpoint types is as follows. The Breakpoint module
gives priority to BDM requests over SWI requests. The external bus
interface tags that pass through the BKP module can only assert BDM
requests.
SWI During a breakpoint, a signal generated by the breakpoint module is
asserted, causing the CPU to execute a SWI instead of the BGND
instruction.
BDM Breakpoints are not allowed if the BDM mode is already active. Active
mode means the CPU is executing out of the BDM ROM. While in BDM
trace mode, tagging into BDM is not allowed.
NOTE: BDM should not be entered from a breakpoint unless the ENABLE bit is
set in the BDM. Even if the ENABLE bit in the BDM is negated, the CPU
actually executes the BDM ROM code. It checks the ENABLE and
returns if enable is not set. If the BDM is not serviced by the monitor, then
the breakpoint would be re-asserted when the BDM returns to normal
CPU flow.
There is no hardware to enforce restriction of breakpoint operation if the
BDM is not enabled.
Modes of Operation
The Breakpoint Module performs the same in all modes of operation.
Table 127 Priority of Forces and Tags
Forces Tags
Force BDM from BDM Module External Bus Interface Tags
Force BDM from BKP Module Breakpoint Module Tags
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