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Clock Generator
Chapter 4
Preliminary User’s Manual U17566EE1V2UM00
4.4.4
Operation of the Clock Monitors
The microcontroller provides two separate clock monitors to watch the activity
of the main oscillator and the sub oscillator.
(1)
Description
The functional block diagram is shown below.
Figure 4-2
Clock Monitors Block Diagram
The clock monitors use the ring oscillator (f
R
) for monitoring the main and sub
oscillators (f
M
).
If the main oscillator clock monitor detects a malfunction of the main oscillator
(no pulse), it generates the reset request RESCMM. If the sub oscillator clock
monitor detects a malfunction of the sub oscillator, it generates the reset
request RESCMS.
(2)
Start and stop
Before the clock monitors can be started, they have to be enabled by setting
CLMM.CLMEM and CLMS.CLMES to 1.
Main oscillator
monitor start
After enabling CLMM.CLMEM = 1 the main oscillator monitor is automatically
started as soon as the main oscillator is stable, indicated by
CGSTAT.OSCSTAT = 1.
Main oscillator
monitor start
After enabling CLMM.CLMES = 1 the sub oscillator monitor must be started by
software by setting CLMCS.CMRT to 1.
After starting the sub oscillator clock monitor by CLMCS.CMRT = 1 clear
CLMCS.CMRT by software.
main osc
CGSTAT.OSCSTAT
start
f
M
f
R
EN
CLKM_MAIN
output
CLMM.CLMEM
RESCMM
sub osc
CLMCS.CMRT
start
f
M
f
R
EN
CLKM_SUB
output
CLMS.CLMES
RESCMS
ring osc
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