Chapter 4 Clock Description
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
97
Figure 4-11. MPC5602PCMU
4.9.2
Main features
•
RC oscillator frequency measurement
•
External oscillator clock monitoring with respect to CK_IRC/
n
clock
•
PLL clock frequency monitoring with respect to CK_IRC/4 clock
•
Event generation for various failures detected inside monitoring unit
4.9.3
Functional description
The clock and frequency names referenced in this block are defined as follows:
•
CK_XOSC: clock coming from the external crystal oscillator
•
CK_IRC: clock coming from the low frequency internal RC oscillator
•
CK_PLL: clock coming from the PLL
•
f
XOSC
: frequency of external crystal oscillator clock
•
f
RC
: frequency of low frequency internal RC oscillator
•
f
PLL
: frequency of FMPLL clock
4.9.3.1
Crystal clock monitor
If f
XOSC
is smaller than f
RC
divided by
2
RCDIV
bits of CMU_0_CSR and the CK_XOSC is ‘ON’ and stable
as signaled by the ME, then:
•
An event pending bit OLRI in CMU_0_ISR is set
•
A failure event OLR is signaled to the RGM and FCU, which in turn can generate either an
interrupt, a reset, or a SAFE mode request.
IRC_CLK
XOSC_CLK
FMPLL_0
16 MHz
4 to 40 MHz
64 MHz
CK 0 (reference)
CK XOSC
CK PLL
XOSC valid (on AND stable) / off
CMU_0
FLL
OLR
FMPLL_0 valid (on AND locked) / off
FCU
FMPLL_0 freq.
out of range
Loss of crystal
Clock
Control
Logic