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EM6621 Datasheet(PDF) 6 Page - EM Microelectronic - MARIN SA

Part No. EM6621
Description  Ultra Low Power Microcontroller with 4x20 LCD Driver
Download  69 Pages
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Maker  EMMICRO [EM Microelectronic - MARIN SA]
Homepage  http://www.emmicroelectronic.com
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EM6621 Datasheet(HTML) 6 Page - EM Microelectronic - MARIN SA

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EM6621
© EM Microelectronic-Marin SA, 03/99, Rev. B/
03/02 REV. D/444
Copyright
 2002, EM Microelectronic-Marin SA
6
www.emmicroelectronic.com
2. Operating Modes
The EM6621 has two low power dissipation modes, standby and sleep.
Figure 4 is a transition diagram for
these modes.
2.1 Active Mode
The active mode is the actual CPU running mode. Instructions are read from the internal ROM and executed by
the CPU. Leaving active mode via the halt instruction to go into standby mode, the Sleep bit write to go into
Sleep mode or a reset from port A to go into reset mode.
2.2 Standby Mode
Executing a halt instruction puts the EM6621
into standby mode. The voltage regulator,
oscillator, watchdog timer, LCD, interrupts,
timers and counters are operating. However,
the CPU stops since the clock related to
instruction execution stops. Registers, RAM
and I/O pins retain their states prior to
standby mode. A reset or an interrupt request
if enabled cancels standby.
2.3 Sleep Mode
Writing to the Sleep bit in the RegSysCntl1
register puts the EM6621 in sleep mode. The
oscillator stops and most functions of the
EM6621 are inactive. To be able to write to
the
Sleep
bit,
the
SleepEn
bit
in
RegSysCntl2 must first be set to "1". In
sleep mode only the voltage regulator and the reset input are active. The RAM data integrity is maintained.
Sleep mode may be canceled only by a high level of min 10µs at the EM6621 Reset terminal or by the selected
port A input reset combination, if option InpResSleep is turned on.
Due to the cold-start characteristics of the oscillator, waking up from sleep mode may take some time to
guarantee stable oscillation. During sleep mode and the following start up the EM6621 is in reset state. Waking
up from sleep clears the Sleep flag but not the SleepEn bit. Inspecting the SleepEn allows to determine if the
EM6621 was powered up (SleepEn = "0") or woken up from sleep (SleepEn = "1").
Table 2.3.1. Internal State in Standby and Sleep Mode
Function
Standby
Sleep
Oscillator
Active
Stopped
Oscillator Watchdog
Active
Stopped
Instruction Execution
Stopped
Stopped
Interrupt Functions
Active
Stopped
Registers and Flags
Retained
Reset
RAM Data
Retained
Retained
Option Registers
Retained
Retained
Timer & Counter
Active
Reset
Logic Watchdog
Active
Reset
I/O Port B and Serial Port
Active
High Impedance,
Pull’s as defined in option register
Input Port A
Active
No pull-downs and inputs deactivated
except if InpResSleep = "1"
LCD
Active
Stopped (display off)
Strobe Output
Active
Active
Buzzer Output
Active
High Impedance
Voltage Level Detector
Finishes ongoing measure, then stop
Stopped
Reset Pin
Active
Active
Figure 4 Mode transition diagram
Active
Halt
instruction
Sleep bit
write
IRQ
Standby
Sleep
Reset=1
Reset=0
Reset=1
Reset=1
Reset


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