MC9S12T64 Datasheet, PDF (560/608 Pages) Motorola, Inc – Specification

Breakpoint (BKP)
Freescale Semiconductor, Inc.
Breakpoint Priority
Breakpoint operation is first determined by the state of BDM. If BDM is
already active, meaning the CPU is executing out of BDM firmware,
Breakpoints are not allowed. In addition, while in BDM trace mode,
tagging into BDM is not allowed. If BDM is not active, the Breakpoint will
give priority to BDM requests over SWI requests. This condition applies
to both forced and tagged breakpoints.
In all cases, BDM related breakpoints will have priority over those
generated by the Breakpoint sub-block. This priority includes
breakpoints enabled by the TAGLO and TAGHI external pins of the
system that interface with the BDM directly and whose signal information
passes through and is used by the Breakpoint sub-block.enabled.
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.
Reset Initialization
The reset state of each individual bit is listed within the Register
Description section, which details the registers and their bit-fields. All
registers are reset by the system reset.
Interrupts
The BKP sub-block causes the CPU to generate SWI interrupts when
BKBDM bit is equal to zero.
MC9S12T64Revision 1.1.1
Breakpoint (BKP)
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