EM78P5840/5841/5842
8-bit Micro-controller
VII.11 Oscillator
The EM78P5840 can be operated in two different oscillator modes, each of them are crystal mode and RC mode.
Users can select one of them by setting code option. The descript of these two oscillator mode are as below:
(1) Crystal mode:
For crystal mode operation, one crystal and tow capacitances is needed for external circuit. In this mode,
eFTP5840 can be run in three active mode include normal mode, green mode and sleep mode. The advantages of this
mode are low power consumption (in green mode) and with more precise main CLK. Next figure show the
application circuit of crystal mode. Pin XIN and pin XOUT can be connected with a crystal directly to generate
oscillation. By clear code option”P70S” to 0, PORT70 can switch to general IO (disable PLL function and
EM78P5840 can not active on normal mode); /RESET pin can switch to PORT71 if clear “P71S” to 0.
XIN
eFHP5840
XOUT
Fig 13: Application circuit of Crystal mode
(CPU stop)
Sleep
M ode
IRC1:ON
32K :un-active
PLL :turnoff
Reset
RA page0bit7=0
& run"SLEP"
Reset
Green
M ode
Normal
M ode
PLLEN bit=1
PLLEN bit=0
RESET
operation
IRC1:ON
32K :oscillating
PLL :turnon
IRC1:ON
32K :oscillating
PLL :turnoff
Resetrelease
Reset
Fig 14: The relative of Crystal mode’s normal, green and sleep mode
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* This specification is subject to change without notice.
34
2004/11/10 V2.6
ELAN [ ELAN MICROELECTRONICS CORP ]
