參數(shù)資料
型號: M38258MCDXXXFP
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 4 MHz, MICROCONTROLLER, PQFP100
封裝: 14 X 20 MM, 0.65 MM PITCH, PLASTIC, QFP-100
文件頁數(shù): 50/73頁
文件大?。?/td> 1323K
代理商: M38258MCDXXXFP
Rev.2.02
Jun 19, 2007
page 52 of 73
REJ03B0146-0202
3823 Group
CLOCK GENERATING CIRCUIT
The 3823 group has two built-in oscillation circuits. An oscillation
circuit can be formed by connecting a resonator between XIN and
XOUT (XCIN and XCOUT). Use the circuit constants in accordance
with the resonator manufacturer's recommended values. The os-
cillation start voltage and the oscillation start time differ in
accordance with an oscillator, a circuit constant, or temperature,
etc.
When power supply voltage is low and the high frequency oscilla-
tor is used, an oscillation start will require sufficient conditions. No
external resistor is needed between XIN and XOUT since a feed-
back resistor exists on-chip. (an external feed-back resistor may
be needed depending on conditions.) However, an external feed-
back resistor is needed between XCIN and XCOUT since a resistor
does not exist between them.
To supply a clock signal externally, input it to the XIN pin and make
the XOUT pin open. The sub-clock XCIN-XCOUT oscillation circuit
cannot directly input clocks that are externally generated. Accord-
ingly, be sure to cause an external resonator to oscillate.
Immediately after poweron, only the XIN oscillation circuit starts
oscillating, and XCIN and XCOUT pins function as I/O ports.
Fig. 55 External clock input circuit
XIN
External oscillation circuit
Open
VCC
VSS
CCIN
CCOUT
Rf
Rd
XCIN
XCOUT
XOUT
Frequency Control
(1) frequency/8 Mode
The internal clock φ is the frequency of XIN divided by 8.
After reset, this mode is selected.
(2) frequency/4 Mode
The internal clock φ is the frequency of XIN divided by 4.
(3) frequency/2 Mode
The internal clock φ is half the frequency of XIN.
(4) Low-speed Mode
●The internal clock φ is the frequency of XIN or on-chip oscillation
frequency divided by 2.
●A low-power consumption operation can be realized by stopping
the main clock XIN in this mode. To stop the main clock, set bit 5
of the CPU mode register to “1”.
When the main clock XIN is restarted, set enough time for oscil-
lation to stabilize by programming.
In low speed mode, the system clock φ can be switched to the
on-chip oscillator or XCIN. Use the on-chip oscillator control bit
(bit 0 in the CPU mode expansion register) for settings. To set
this bit to “0” from “1”, wait until XCIN oscillation stabilizes.
Note 1: If you switch the mode between frequency/2/4/8 mode
and low-speed, stabilize both XIN and XCIN oscillations.
The sufficient time is required for the sub-clock to stabi-
lize, especially immediately after poweron and at
returning from stop mode. When switching the mode be-
tween middle/high-speed and low-speed, set the
frequency on condition that f(XIN) > 3f(XCIN).
2: In frequency/2/4/8 mode, XIN-XOUT oscillation does not
stop even if the main clock (XIN-XOUT) stop bit is set to
"1".
3: In low speed mode, XCIN-XCOUT oscillation does not stop
even if the port XC switch bit is set to "0".
Fig. 54 Ceramic resonator circuit example
XCIN XCOUT
XIN
XOUT
CIN
COUT
CCIN
CCOUT
Rf
Rd
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 feedback
resistor
between XIN and XOUT following the instruction.
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