Chapter 36 Nexus Development Interface (NDI)
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
917
36.12.6 Access to Debug Resources
Resources contained in the e200z0h OnCE Module which do not require the e200z0h processor core to be
halted for access may be accessed while the e200z0h core is running, and will not interfere with processor
execution. Accesses to other resources such as the CPUSCR require the e200z0h core to be placed in
debug mode to avoid synchronization hazards. Debug firmware may ensure that it is safe to access these
resources by determining the state of the e200z0h core prior to access. Note that a scan operation to update
the CPUSCR is required prior to exiting debug mode if debug mode has been entered.
Some cases of write accesses other than accesses to the OnCE Command and Control registers, or the
EDM bit of DBCR0 require the e200z0h
m_clk
to be running for proper operation. The OnCE control
register provides a means of signaling this need to a system level clock control module.
In addition, since the CPU may cause multiple bits of certain registers to change state, reads of certain
registers while the CPU is running (DBSR, etc.) may not have consistent bit settings unless read twice with
the same value indicated. In order to guarantee that the contents are consistent, the CPU should be placed
into debug mode, or multiple reads should be performed until consistent values have been obtained on
consecutive reads.
29
WKUP
Wakeup Request Bit (WKUP)
This control bit may be used to force the e200z0h
p_wakeup
output signal to be asserted.
This control function may be used by debug firmware to request that the chip-level clock
controller restore the
m_clk
input to normal operation regardless of whether the CPU is in a
low power state to ensure that debug resources may be properly accessed by external
hardware through scan sequences.
30
FDB
Force Breakpoint Debug Mode Bit (FDB)
This control bit is used to determine whether the processor is operating in breakpoint debug
enable mode or not. The processor may be placed in breakpoint debug enable mode by
setting this bit. In breakpoint debug enable mode, execution of the ‘
bkpt
’ pseudo-instruction
will cause the processor to enter debug mode, as if the
jd_de_b
input had been asserted.
This bit is qualified with DBCR0
EDM
, which must be set for FDB to take effect.
31
DR
CPU Debug Request Control Bit
This control bit is used to unconditionally request the CPU to enter the Debug Mode. The
CPU will indicate that Debug Mode has been entered via the data scanned out in the shift-IR
state.
0 – No Debug Mode request
1 – Unconditional Debug Mode request
When the DR bit is set the processor will enter Debug mode at the next instruction boundary.
1
Unused by Z0Hn2p
Table 36-13. OnCE Control Register Bit Definitions (continued)
Bit(s)
Name
Description