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5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Oscillation Circuits and Operating Mode)
5.3 Oscillation Circuits and
Operating Mode
5.3.1 Configuration of oscillation circuits
The E0C88832/88862 is twin clock system with two
internal oscillation circuits (OSC1 and OSC3).
OSC1 oscillation circuit generates the 32.768 kHz
(Typ.) main clock and OSC3 oscillation circuit the
sub-clock when the CPU and some peripheral
circuits (output port, serial interface and program-
mable timer) are in high speed operation.
Figure 5.3.1.1 shows the configuration of the
oscillation circuit.
OSC1
oscillation circuit
OSC3
oscillation circuit
Oscillation circuit
control signal
SLEEP
OSCC
status
Fig. 5.3.1.1 Configuration of oscillation circuits
At initial reset, OSC1 oscillation circuit is selected
for the CPU operating clock and OSC3 oscillation
circuit is in a stopped state. ON/OFF switching of
the OSC3 oscillation circuit and switching of the
system clock between OSC1 and OSC3 are control-
led in software. OSC3 circuit is utilized when high
speed operation of the CPU and some peripheral
circuits become necessary. Otherwise, OSC1 should
be used to generate the operating clock and OSC3
circuit placed in a stopped state in order to reduce
current consumption.
5.3.2 Mask option
OSC1 oscillation circuit
Crystal oscillation circuit
External clock input
CR oscillation circuit
Crystal oscillation circuit
OSC3 oscillation circuit
Crystal oscillation circuit
Ceramic oscillation circuit
CR oscillation circuit
External clock input
In terms of the oscillation circuit types for OSC1,
either crystal oscillation, CR oscillation, crystal
oscillation (gate capacitor built-in) or external clock
input can be selected with the mask option.
In terms of oscillation circuit types for OSC3, either
crystal oscillation, ceramic oscillation, CR oscilla-
tion or external clock input can be selected with the
mask option, in the same way as OSC1.
28
To peripheral
circuit (f
)
OSC1
Clock
To CPU (CLK)
switch
To some peripheral
circuit (f
)
OSC3
CPU clock
selection signal
CLKCHG
(gate capacitor built-in)
5.3.3 OSC1 oscillation circuit
The OSC1 oscillation circuit generates the 32.768 kHz
(Typ.) system clock which is utilized during low
speed operation (low power mode) of the CPU and
peripheral circuits. Furthermore, even when OSC3 is
utilized as the system clock, OSC1 continues to
generate the source clock for the clock timer and
stopwatch timer.
This oscillation circuit stops when the SLP instruc-
tion is executed. However, in case the SVD circuit is
executing an SLP instruction, oscillation is stopped
in synchronization with the completion of sampling.
In terms of the oscillation circuit types, either
crystal oscillation, CR oscillation, crystal oscillation
(gate capacitor built-in) or external clock input can
be selected with the mask option.
Figure 5.3.3.1 shows the configuration of the OSC1
oscillation circuit.
OSC1
C
G1
X'tal1
OSC2
V
SS
(1) Crystal oscillation circuit
OSC1
V
DD
V
SS
External
clock
N.C.
OSC2
(2) External clock input
OSC1
R
CR1
OSC2
(3) CR oscillation circuit
OSC1
X'tal1
OSC2
(4) Crystal oscillation circuit (gate capacitor built-in)
Fig. 5.3.3.1 OSC1 oscillation circuit
EPSON
SLEEP status
f
OSC1
V
SS
SLEEP status
f
OSC1
V
SS
f
OSC1
SLEEP status
SLEEP status
f
OSC1
V
SS
V
SS
E0C88832/88862 TECHNICAL MANUAL
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