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参数资料
| 型号： | M38748EAF-XXXFS |
| 厂商： | Mitsubishi Electric Corporation |
| 英文描述： | SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| 中文描述： | 单芯片8位CMOS微机 |
| 文件页数： | 62/92页 |
| 文件大小： | 1292K |
| 代理商： | M38748EAF-XXXFS |
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62
3874 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
CLOCK GENERATING CIRCUIT
The 3874 group has two built-in oscillation circuits. An oscillation
circuit can be formed by connecting a resonator between X
IN
and
X
OUT
(X
CIN
and X
COUT
). Use the circuit constants in accordance
with the resonator manufacturer’s recommended values. No exter-
nal resistor is needed between X
IN
and X
OUT
since a feed-back
resistor exists on-chip. However, an external feed-back resistor is
needed between X
CIN
and X
COUT
.
Immediately after power on, only the X
IN
oscillation circuit starts
oscillating, and X
CIN
and X
COUT
pins function as I/O ports.
When using the X
CIN
oscillation circuit, X
CIN
and X
COUT
pins’ pull-
up resistors need to be invarid.
Frequency Control
(1) Middle-speed mode
The internal clock
φ
is the frequency of X
IN
divided by 8. After re-
set, this mode is selected.
(2) Double-speed mode
The internal clock
φ
is the frequency of X
IN
.
(3) High-speed mode
The internal clock
φ
is half the frequency of X
IN
.
(4) Low-speed mode
The internal clock
φ
is half the frequency of X
CIN
.
I
Note
When switching the mode between double/middle/high-speed and
low-speed, stabilize both X
IN
and X
CIN
oscillations. Sufficient time
is required for the sub clock to stabilize, especially immediately af-
ter power on and at returning from stop mode. When switching the
mode between double/middle/high-speed and low-speed, set the
frequency on condition that f(X
IN
) > 3f(X
CIN
).
It takes the cycle number mentioned below to switch between
each mode (machine cycle = cycle of internal clock
φ
).
Double-speed mode
→
Except double-speed mode
1 to 8 machine cycles
High-speed mode
→
Except high-speed mode
1 to 4 machine cycles
Middle-speed mode
→
Except middle-speed mode
1 machine cycle
Low-speed mode
→
Except low-speed mode
1 to 4 machine cycles
The 3874 group operates in the previous mode while the mode is
switched.
(5) Low power dissipation mode
The low power consumption operation can be realized by stopping
the main clock X
IN
in low-speed mode. To stop the main clock, set
bit 5 of the CPU mode register to “1”. When the main clock X
IN
is
restarted (by setting the main clock stop bit to “0”), set sufficient
time for oscillation to stabilize.
By clearing furthermore the X
COUT
drivability selection bit (b3) of
the CPU mode register to “0”, low power consumption operation
can be realized by reducing the drivability between X
CIN
and
X
COUT
. At reset or during STP instruction execution this bit is set
to “1” and a reduced drivability that has an easy oscillation start is
set. The sub-clock X
CIN
-X
COUT
oscillating circuit can no directly in-
put clocks that are generated externally. Accordingly, make sure to
cause an external resonator to oscillate.
Oscillation Control
(1) Stop mode
When the STP instruction is executed, the internal clock
φ
stops at
an “H” level, and X
IN
and X
CIN
oscillators stop. The value set to the
timer 1 latch and the timer 2 latch is set to timer 1 and timer 2. Ei-
ther X
IN
or X
CIN
divided by 16 is input to timer 1 as count source,
and the output of timer 1 is connected to timer 2. The bits of the
timer 123 mode register except the timer 3 count source selection
bit (b4) are cleared to “0”. Set the interrupt enable bits of timer 1
and timer 2 to the disabled state (“0”) before executing the STP in-
struction.
Oscillator restarts at reset or when an external interrupt is re-
ceived, but the internal clock
φ
is not supplied to the CPU until
timer 2 underflows. This allows time for the clock circuit oscillation
to stabilize. Timer 1 latch and timer 2 latch should be set to proper
values for stabilizing oscillation before executing the STP instruc-
tion.
(2) Wait mode
If the WIT instruction is executed, the internal clock
φ
stops at an
“H” level. The states of X
IN
and X
CIN
are the same as the state be-
fore executing the WIT instruction. The internal clock
φ
restarts at
reset or when an interrupt is received. Since the oscillator does
not stop, normal operation can be started immediately after the
clock is restarted.
Fig. 68 Ceramic resonator circuit
Fig. 69 External clock input circuit
X
CIN
X
COUT
X
IN
X
OUT
C
IN
C
OUT
C
CIN
C
COUT
Rf
Rd
X
CIN
X
COUT
X
IN
X
OUT
Open
External oscillation
circuit
C
COUT
V
CC
V
SS
C
CIN
Rf
Rd
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|---|---|
| M38748EAF-XXXGP | SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
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| M38748EDF-XXXFS | SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| M38748EAF-XXXGP | 制造商:MITSUBISHI 制造商全称:Mitsubishi Electric Semiconductor 功能描述:SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| M38748EAT-XXXFS | 制造商:MITSUBISHI 制造商全称:Mitsubishi Electric Semiconductor 功能描述:SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| M38748EAT-XXXGP | 制造商:MITSUBISHI 制造商全称:Mitsubishi Electric Semiconductor 功能描述:SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| M38748EBD-XXXFS | 制造商:MITSUBISHI 制造商全称:Mitsubishi Electric Semiconductor 功能描述:SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| M38748EBD-XXXGP | 制造商:MITSUBISHI 制造商全称:Mitsubishi Electric Semiconductor 功能描述:SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
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