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Chapter 11 S12XE Clocks and Reset Generator (S12XECRGV1) Block Description
MC9S12XE-Family Reference Manual Rev. 1.07
Freescale Semiconductor
487
5, 4
FM1, FM0
IPLL
Frequency Modulation Enable Bit
— FM1 and FM0 enable additional frequency modulation on the
VCOCLK. This is to reduce noise emission. The modulation frequency is f
ref
divided by 16. Write anytime except
when PLLSEL = 1. See
Table 11-7
for coding.
3
FSTWKP
Fast Wake-up from Full Stop Bit
— FSTWKP enables fast wake-up from full stop mode. Write anytime. If
Self-Clock Mode is disabled (SCME = 0) this bit has no effect.
0 Fast wake-up from full stop mode is disabled.
1 Fast wake-up from full stop mode is enabled. When waking up from full stop mode the system will immediately
resume operation in Self-Clock Mode (see
Section 11.4.1.4, “Clock Quality Checker”
). The SCMIF flag will not
be set. The system will remain in Self-Clock Mode with oscillator and clock monitor disabled until FSTWKP bit
is cleared. The clearing of FSTWKP will start the oscillator, the clock monitor and the clock quality check. If
the clock quality check is successful, the S12XECRG will switch all system clocks to OSCCLK. The SCMIF
flag will be set. See application examples in
Figure 11-19
and
Figure 11-20
.
2
PRE
RTI Enable During Pseudo Stop Bit
— PRE enables the RTI during Pseudo Stop Mode.
Write anytime.
0 RTI stops running during Pseudo Stop Mode.
1 RTI continues running during Pseudo Stop Mode.
Note:
If the PRE bit is cleared the RTI dividers will go static while Pseudo Stop Mode is active. The RTI dividers
will not initialize like in Wait Mode with RTIWAI bit set.
1
PCE
COP Enable During Pseudo Stop Bit
— PCE enables the COP during Pseudo Stop Mode.
Write anytime.
0 COP stops running during Pseudo Stop Mode
1 COP continues running during Pseudo Stop Mode
Note:
If the PCE bit is cleared the COP dividers will go static while Pseudo Stop Mode is active. The COP
dividers will not initialize like in Wait Mode with COPWAI bit set.
0
SCME
Self Clock Mode Enable Bit
Normal modes: Write once
Special modes: Write anytime
SCME can not be cleared while operating in Self Clock Mode (SCM = 1).
0 Detection of crystal clock failure causes clock monitor reset (see
Section 11.5.1.1, “Clock Monitor Reset”
).
1 Detection of crystal clock failure forces the MCU in Self Clock Mode (see
Section 11.4.2.2, “Self Clock Mode”
).
Table 11-7. FM Amplitude selection
FM1
FM0
FM Amplitude /
f
VCO
Variation
0
0
FM off
0
1
±
1%
1
0
±
2%
1
1
±
4%
Table 11-6. PLLCTL Field Descriptions (continued)
Field
Description