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7542 Group
Clock Generating Circuit
An oscillation circuit can be formed by connecting a resonator be-
tween X
and X
, and an RC oscillation circuit can be formed
IN
OUT
by connecting a resistor and a capacitor.
Use the circuit constants in accordance with the resonator
manufacturer's recommended values.
No external resistor is needed between X
feed-back resistor exists on-chip. (An external feed-back resistor
may be needed depending on conditions.)
(1) On-chip oscillator operation
When the MCU operates by the on-chip oscillator for the main
clock, connect X
pin to V
IN
CC
pin open.
The clock frequency of the on-chip oscillator depends on the sup-
ply voltage and the operation temperature range.
Be careful that variable frequencies when designing application
products.
(2) Ceramic resonator
When the ceramic resonator is used for the main clock, connect
the ceramic resonator and the external circuit to pins X
X
at the shortest distance. A feedback resistor is built in be-
OUT
tween pins X
and X
.
IN
OUT
(3) RC oscillation
When the RC oscillation is used for the main clock, connect the
X
pin and X
pin to the external circuit of resistor R and the
IN
OUT
capacitor C at the shortest distance.
The frequency is affected by a capacitor, a resistor and a micro-
computer.
So, set the constants within the range of the frequency limits.
(4) External clock
When the external signal clock is used for the main clock, connect
the X
pin to the clock source and leave X
IN
Select "0" (ceramic oscillation) to oscillation mode selection bit of
CPU mode register (003B
).
16
Rev.3.02
Oct 31, 2006
REJ03B0006-0302
and X
since a
IN
OUT
through a resistor and leave X
pin open.
OUT
Page 60 of 134
X
I N
R
Fig. 73 Processing of X
operation
OUT
and
IN
Note:
Insert a damping resistor if required.
The resistance will vary depending on the oscillator and
the oscillation drive capacity setting.
Use the value recommended by the maker of the oscillator.
Also, if the oscillator manufacturer's data sheet specifies
that a feedback resistor be added external to the chip
though a feedback resistor exists on-chip, insert a feed-
back resistor between X
instruction.
Fig. 74 External circuit of ceramic resonator
M37542
X
I N
Fig. 75 External circuit of RC oscillation
External oscillation
circuit
Fig. 76 External clock input circuit
Note:
The clock frequency of the
on-chip oscillator depends
M37542
on the supply voltage and
the operation temperature
range.
X
O U T
Be careful that variable
frequencies and obtain
O p e n
the sufficient margin.
and X
pins at on-chip oscillator
IN
OUT
M37542
X
X
IN
OUT
Rd
C
C
I N
OUT
and X
IN
OUT
Note:
Connect the external
circuit of resistor R
and the capacitor C at
the shortest distance.
X
O U T
The frequency is af-
fected by a capacitor,
R
a resistor and a micro-
computer.
C
So, set the constants
within the range of the
frequency limits.
M37542
X
X
IN
OUT
O p e n
V
C C
V
SS
following the
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