Chapter 7 Mode Entry Module (MC_ME)
MPC5602P Microcontroller Reference Manual, Rev. 4
172
Freescale Semiconductor
7.4.4
Protection of Mode Configuration Registers
While programming the mode configuration registers ME_<mode>_MC, the following rules must be
respected. Otherwise, the write operation is ignored and an invalid mode configuration interrupt may be
generated.
•
If the 16 MHz int. RC osc. is selected as the system clock, 16 MHz_IRC must be on.
•
If the 4 MHz crystal osc. clock is selected as the system clock, OSC must be on.
•
If the system PLL clock is selected as the system clock, PLL must be on.
•
The 4 MHz crystal oscillator must be on if the system PLL is on. Therefore, when writing a ‘1’ to
PLL0ON, a ‘1’ must also be written to XOSC0ON.
NOTE
Software must ensure that clock sources with dependencies other than those
mentioned above are swithced on as needed. There is no automatic
protection mechanism to check this in the MC_ME.
•
Configuration “00” for the CFLAON and DFLAON bit fields is reserved.
•
Configuration “10” for the DFLAON bit field is reserved.
•
If the DFLAON bit field is set to “11”, the CFLAON field must also be set to “11”.
•
System clock configurations marked as ‘reserved’ may not be selected.
•
Configuration “1111” for the SYSCLK bit field is allowed only for theTEST mode, and only in this
case may all system clock sources be turned off.
WARNING
If the system clock is stopped during TEST mode, the device can exit only
via a system reset.
7.4.5
Mode Transition Interrupts
The MC_ME provides interrupts for incorrectly configuring a mode, requesting an invalid mode
transition, indicating a SAFE mode transition not due to a software request, and indicating when a mode
transition has completed.
7.4.5.1
Invalid Mode Configuration Interrupt
Whenever a write operation is attempted to the ME_<mode>_MC registers violating the protection rules
mentioned in the
Section 7.4.4, “Protection of Mode Configuration Registers
I_ICONF of the ME_IS register is set and an interrupt request is generated if the mask bit M_ICONF of
ME_IM register is ‘1’.
7.4.5.2
Invalid Mode Transition Interrupt
The mode transition request is considered invalid under the following conditions: