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6.2 Precautions on Mounting
<Oscillation Circuit>
Oscillation characteristics change depending on
conditions (board pattern, components used,
etc.).
In particular, when a ceramic or crystal
oscillator is used, use the oscillator
manufacturer's recommended values for
constants such as capacitance and resistance.
Disturbances of the oscillation clock due to
noise may cause a malfunction. Consider the
following points to prevent this:
(1) Components which are connected to the
OSC1, OSC2, OSC3 and OSC4 terminals,
such as oscillators, resistors and capacitors,
should be connected in the shortest line.
(2) As shown in the right hand figure, make a
V
pattern as large as possible at circum-
SS
scription of the OSC1, OSC2, OSC3 and
OSC4 terminals and the components
connected to these terminals.
Furthermore, do not use this V
any purpose other than the oscillation
system.
Sample V
pattern (OSC3)
SS
In order to prevent unstable operation of the
oscillation circuit due to current leak between
OSC1/OSC3 and V
DD
distance between OSC1/OSC3 and V
signals on the board pattern.
<Reset Circuit>
The power-on reset signal which is input to the
RESET terminal changes depending on
conditions (power rise time, components used,
board pattern, etc.).
Decide the time constant of the capacitor and
resistor after enough tests have been completed
with the application product.
When the built-in pull-up resistor of the RESET
terminal is used, take into consideration
dispersion of the resistance for setting the
constant.
In order to prevent any occurrences of unneces-
sary resetting caused by noise during operating,
components such as capacitors and resistors
should be connected to the RESET terminal in
the shortest line.
S1C88650 TECHNICAL MANUAL
pattern for
SS
OSC4
OSC3
V
SS
, please keep enough
or other
DD
<Power Supply Circuit>
Sudden power supply variation due to noise
may cause malfunction. Consider the following
points to prevent this:
(1) The power supply should be connected to
the V
and V
DD
short and large as possible.
(2) When connecting between the V
terminals with a bypass capacitor, the
terminals should be connected as short as
possible.
Bypass capacitor connection example
(3) Components which are connected to the
V
, V
, V
D1
C1
such as capacitors and resistors, should be
connected in the shortest line.
In particular, the V
voltages affect the display quality.
<Arrangement of Signal Lines>
In order to prevent generation of
electromagnetic induction noise caused by
mutual inductance, do not arrange a large
current signal line near the circuits that are
sensitive to noise such as the oscillation unit.
When a signal line is parallel with a high-speed
line in long distance or intersects a high-speed
line, noise may generated by mutual
interference between the signals and it may
cause a malfunction.
Do not arrange a high-speed signal line
especially near circuits that are sensitive to
noise such as the oscillation unit.
Prohibited pattern
Large current signal line
High-speed signal line
EPSON
6 SUMMARY OF NOTES
terminal with patterns as
SS
DD
V
V
DD
V
V
SS
, V
, V
and V
terminals,
C2
C3
C4
C5
, V
, V
, V
C1
C2
C3
C4
OSC4
OSC3
V
SS
and V
SS
DD
SS
and V
C5
137
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