參數(shù)資料
型號(hào): M37548G1FP
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 8 MHz, MICROCONTROLLER, PDSO20
封裝: 4.40 X 6.50 MM, 0.65 MM PITCH, PLASTIC, LSSOP-20
文件頁數(shù): 41/84頁
文件大?。?/td> 1427K
代理商: M37548G1FP
Rev.2.02
Mar 31, 2009
Page 46 of 81
REJ03B0210-0202
7548 Group
Clock Generating Circuit
The clock generating circuit includes the XIN clock (ceramic
oscillator or crystal oscillator can be used), XCIN clock (32 kHz
oscillator can be used), external clock input, high-speed on-chip
oscillator, and low-speed on-chip oscillator.
Pins P20/XOUT/XCOUT and P21/XIN/XCIN can be shared for the
ports, XIN oscillation, and XCIN oscillation.
Use the oscillation method selection bits (bits 1 and bit 0 in
function set ROM data 1 (FSROM1)) to set the function of these
pins.
Ceramic Resonator or Crystal Oscillator
Set the oscillation method selection bits (bits 1 and bit 0 in
FSROM1) to “012”, and connect the ceramic resonator (or the
oscillator) and external circuit with the shortest wiring length
possible.
The constants of the oscillator circuit differ depending on the
resonator. Use the values recommended by the resonator
manufacturer. (An external feedback resistor may be necessary
under some conditions.)
Setting the XIN/XCIN oscillation control bit to “0” starts
oscillation. This bit is sets to “0” after reset.
32 kHz Crystal Oscillator
Set the oscillation method selection bits to “102”, and connect the
32 kHz crystal oscillator and external circuit with the shortest
wiring length possible.
The constants of the oscillator circuit differ depending on the
resonator. Use the values recommended by the resonator
manufacturer. (An external feedback resistor may be necessary
under some conditions.)
Setting the XIN/XCIN oscillation control bit to “0” starts
oscillation. This bit is sets to “0” after reset.
External Clock Input
Set the oscillation method selection bits to “112”, and connect the
clock source to the P20/XOUT pin. In this case, the P21/XIN pin
can be used as an I/O port.
High-Speed On-Chip Oscillator
The high-speed on-chip oscillator is stopped after reset.
Setting the high-speed on-chip oscillator oscillation control bit
(bit 1 in CLKM) to “0” starts oscillation. This bit is sets to “1”
after reset.
Low-Speed On-Chip Oscillator
The low-speed on-chip oscillator automatically starts oscillating
after reset.
Setting the low-speed on-chip oscillator oscillation control bit
(bit 0 in CLKM) to “1” stops oscillation. This bit is sets to “0”
after reset. If the low-speed on-chip oscillator control bit (bit 4 in
FSROM2) is set to “0” and stopping the low-speed on-chip
oscillator is disabled, the low-speed on-chip oscillator oscillation
control bit cannot be set to “1” and oscillation cannot be stopped.
Also, the oscillator does not stop even when the STP instruction
is executed.
Using No Oscillator Pins (P20 as output port and P21
as I/O port)
To use only an internal on-chip oscillator, set the oscillation
method selection bits to “002”. The P20/XOUT pin can be used as
an output port and the P21/XIN pin can be used as an I/O port.
Fig 61. Structure of function set ROM data 1
Fig 62. External circuit of ceramic resonator
Fig 63. External circuit of 32 kHz quarts-crystal
oscillator
Fig 64. External clock input circuit
Oscillation method select bits (Note 1)
b1 b0
0 0: No resonator used (P20 and P21 set as I/O ports)
0 1: Ceramic resonator or quartz-crystal oscillation
1 0: 32 kHz quartz-crystal oscillation
1 1: External clock input (P21 set as I/O port)
Stop mode low voltage detection circuit enable/disable bit
(Note 2)
0: Low voltage detection circuit disabled in stop mode
1: Low voltage detection circuit enabled in stop mode
Always set these bits to 0.
Always set this bit to 1.
b7
Function set ROM data 1
FSROM1 (FFD916)
b0
Notes 1: The P20/XOUT and P21/XIN pins build in an on-chip oscillator. Even if these
pins are used as I/O ports, the oscillator circuit is enabled when the MCU’s Vcc
voltage drops below the operation limit voltage. In this case these pins may output
undefined values.
2: If the low voltage detection circuit is enabled in stop mode, power consumption in
stop mode will increase.
M37548
XIN
XOUT
Rd
COUT
CIN
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.
M37548
XCIN
XCOUT
Rd
C COUT
C CIN
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.
M37548
P21
XOUT
I/O port
External
oscillation circuit
Vcc
Vss
Connect the external clock
to the P20/XOUT pin, not
the P21/XIN pin.
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