Chapter 7 S12 Clock, Reset and Power Management Unit (S12CPMU_UHV_V5)
S12ZVHY/S12ZVHL Family Reference Manual, Rev. 1.05
Freescale Semiconductor
289
Three control bits in the CPMUCOP register allow selection of seven COP time-out periods.
When COP is enabled, the program must write $55 and $AA (in this order) to the CPMUARMCOP
register during the selected time-out period. Once this is done, the COP time-out period is restarted. If the
program fails to do this and the COP times out, a COP reset is generated. Also, if any value other than $55
or $AA is written, a COP reset is generated.
Windowed COP operation is enabled by setting WCOP in the CPMUCOP register. In this mode, writes to
the CPMUARMCOP register to clear the COP timer must occur in the last 25% of the selected time-out
period. A premature write will immediately reset the part.
In MCU Normal Mode the COP time-out period (CR[2:0]) and COP window (WCOP) setting can be
automatically pre-loaded at reset release from NVM memory (if values are defined in the NVM by the
application). By default the COP is off and no window COP feature is enabled after reset release via NVM
memory. The COP control register CPMUCOP can be written once in an application in MCU Normal
Mode to update the COP time-out period (CR[2:0]) and COP window (WCOP) setting loaded from NVM
memory at reset release. Any value for the new COP time-out period and COP window setting is allowed
except COP off value if the COP was enabled during pre-load via NVM memory.
The COP clock source select bits can not be pre-loaded via NVM memory at reset release. The IRC clock
is the default COP clock source out of reset.
The COP clock source select bits (COPOSCSEL0/1) and ACLK clock control bit in Stop Mode (CSAD)
can be modified until the CPMUCOP register write once has taken place. Therefore these control bits
should be modified before the final COP time-out period and window COP setting is written.
The CPMUCOP register access to modify the COP time-out period and window COP setting in MCU
Normal Mode after reset release must be done with the WRTMASK bit cleared otherwise the update is
ignored and this access does not count as the write once.
7.5.6
Power-On Reset (POR)
The on-chip POR circuitry detects when the internal supply VDD drops below an appropriate voltage
level. The POR is deasserted, if the internal supply VDD exceeds an appropriate voltage level (voltage
levels not specified, because the internal supply can not be monitored externally).The POR circuitry is
always active. It acts as LVR in Stop Mode.
7.5.7
Low-Voltage Reset (LVR)
The on-chip LVR circuitry detects when one of the supply voltages VDD, VDDX and VDDF drops below
an appropriate voltage level. If LVR is deasserted the MCU is fully operational at the specified maximum
speed. The LVR assert and deassert levels for the supply voltage VDDX are V
LVRXA
and V
LVRXD
and are
specified in the device Reference Manual.The LVR circuitry is active in Run- and Wait Mode.
