EM78P5840N/41N/42N
8-Bit Microcontrollers
7.11 Oscillator
The EM78P5840N/41N/42N can be operated in three different oscillator modes; i.e.,
Crystal mode, IRC mode, and ERIC mode. The modes can be selected by setting the
code option accordingly. The following sections describe in details the three oscillator
modes.
7.11.1 Crystal Mode
To operate in Crystal mode, one crystal and two capacitors are needed for the external
circuit. In this mode, the EM78P5840N/41N/42N can run in three active modes, i.e.,
Normal mode, Green mode, and Sleep mode. The advantages of Crystal mode
opeation are low power consumption (in Green mode) and a more accurate main CLK.
The following figure shows the Crystal mode application circuit. Pin XIN and Pin XOUT
can be directly connected to a crystal to generate an oscillation. By clearing the code
option “P70S” to “0,” Port 70 will switch and operate as a general I/O (the PLL function
must be disabled to prevent activating the Normal mode). The /RESET pin will switch
to Port 71 if “P71S” is cleared to “0.”
XIN
EM78P5840N
XOUT
Figure 7-10a Crystal Mode Application Circuit
(CPU stop)
Sleep
Mode
32K : un-active
PLL : turn off
Reset
RA page0 bit7 = 0
& run"SLEP"
Reset
Green
Mode
Normal
Mode
PLLEN bit = 1
PLLEN bit = 0
RESET
operation
32K : oscillating
PLL : turn off
32K : oscillating
PLL : turn off
Reset release
Reset
Figure 6-10b Correlation between Normal, Green, and Sleep Modes in Crystal Mode
Product Specification (V1.0) 04.25.2006
(This specification is subject to change without further notice)
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ELAN [ ELAN MICROELECTRONICS CORP ]
