7 clock generation, 8 power modes, 2 .7 clock generation -14 2 .8 power modes -14 – Maxim Integrated MAX31782 User Manual
Page 18: 7clockgeneration, 8powermodes
MaximIntegrated 2-14
MAX31782 User’s Guide
Revision 0; 8/11
2.7ClockGeneration
The MAX31782 generates its 4MHz instruction clock using an internal oscillator . This oscillator starts up when V
DD
exceeds the brownout voltage level, V
BO
. There is a delay of approximately 1000 clock cycles (t
SU:MOSC
) between
when the oscillator starts and when clocking of the MAX31782 begins . This delay ensures that the clock is stable prior
to beginning normal operation .
2.8PowerModes
The MAX31782 has two modes of operation . These two modes of operation are detailed in the state diagram as shown
in
.
1) Normal CPU mode
2) Stop mode
The MAX31782 enters stop mode when the STOP bit in the system clock control register (CKCN) is set . Upon entering
stop mode, the digital core is no longer clocked, thus making the core inactive . In stop mode, the ADC is also disabled
and the Supply Voltage Monitor (SVM) can be disabled . The internal oscillator, brownout detection, and regulators
(REG18 and REG25 pins) remain active during stop mode .
details the state of the MAX31782’s analog and
digital blocks during the different modes of operation .
The MAX31782 exits stop mode when any of the following interrupt conditions occurs:
• GPIO interrupt from Port 6
• I
2
C START interrupt
• SVM interrupt
• External reset
The interrupt sources listed must be enabled prior to entering stop mode if they are going to be used to bring the
MAX31782 out of stop mode . After receiving one of these interrupts, the MAX31782 exits stop mode and returns to CPU
mode within 10 system clock cycles . If an interrupt causes the system to come out of stop mode, the program execution
starts from the point where stop mode was asserted . However, if an external reset is used to come out of stop mode,
the program execution begins from utility ROM location 8000h .
Table2-2.StateofCircuitsDuringDifferentModes
CKCN.STOP
SVM.SVMEN
SVM.SVMSTOP
POWER
MODE
CPU
REGULATORS
INTERNAL
OSCILLATOR
BROWNOUT
DETECTION
SVM
MONITOR
ADC
1.8V
2.5V
0
0
X
CPU
Mode
On
On
On
On
On
Off
On/Off
0
1
X
CPU
Mode
On
On
On
On
On
On
On/Off
1
0
X
Stop
Mode
Off
On
On
On
On
Off
Off
1
1
0
Stop
Mode
Off
On
On
On
On
Off
Off
1
1
1
Stop
Mode
Off
On
On
On
On
On
Off