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参数资料
| 型号： | M38C80ED-XXXFP |
| 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： | 37/51页 |
| 文件大小： | 874K |
| 代理商： | M38C80ED-XXXFP |
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37
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
38C8 Group
PRELIMINARY
Notice: This is not a final specification.
change.
Some parametric limits are subject to
CLOCK GENERATING CIRCUIT
The 38C8 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
). RC oscillation is available for X
IN
-X
OUT
.
Immediately after power on, only the X
IN
oscillation circuit starts os-
cillating, and X
CIN
and X
COUT
pins go to high impedance state.
Main Clock
An oscillation circuit by a resonator can be formed by setting the
OSCSEL pin is set to
“
L
”
level and connecting a resonator between
X
IN
and X
OUT.
Use the circuit constants in accordance with the reso-
nator manufacturer
’
s recommended values. No external resistor is
needed between X
IN
and X
OUT
since a feed-back resistor exists on-
chip. To supply a clock signal externally, make the X
OUT
pin open in
the
“
L
”
level state of the OSCSEL pin, and supply the clock from the
X
IN
pin. The RC oscillation circuit can be formed by setting the
OSCSEL pin to
“
H
”
level and connecting a resistor between the X
IN
pin and the X
OUT
pin. At this time, the feed-back resistor is cut off.
The frequency of the RC oscillation changes owing to a parasitic
capacitance or the wiring length etc. of the printed circuit board. Do
not use the RC oscillation in the usage which the frequency accuracy
of the main clock is needed.
Sub-clock
Connect a resonator between X
CIN
and X
COUT
. An external feed-
back resistor is needed between X
CIN
and X
COUT
since a feed-back
resistor does not exist on-chip. The sub-clock X
CIN
-X
COUT
oscillation
circuit cannot directly input clocks that are externally generated. Ac-
cordingly, be sure to cause an external resonator to oscillate.
Frequency Control
(1) Middle-speed Mode
The internal clock
φ
is the frequency of X
IN
divided by 8. At reset, this
mode is selected.
(2) High-speed Mode
The internal clock
φ
is the frequency of X
IN
divided by 2.
(3) Low-speed Mode
The internal clock
φ
is the frequency of X
CIN
divided by 2.
A low-power consumption operation can be realized by stopping the
main clock X
IN
in this mode. To stop the main clock, set bit 5 of the
CPU mode register to
“
1
”
. When the main clock X
IN
is restarted, set
enough time for oscillation to stabilize by programming.
I
Notes on clock generating circuit
If you switch the mode between middle/high-speed and low-speed,
stabilize both X
IN
and X
CIN
oscillations. The sufficient time is required
for the sub clock to stabilize, especially immediately after power on
and at returning from stop mode. When switching the mode between
middle/high-speed and low-speed, set the frequency on condition
that f(X
IN
) > 3
f(X
CIN
).
Oscillation Control
(1) Stop Mode
If the STP instruction is executed, the internal clock
φ
stops at an
“
H
”
level, and X
IN
and X
CIN
oscillators stop. Timer 1 is set to
“
FF
16
”
and
timer 2 is set to
“
01
16
.
”
Either X
IN
divided by 16 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 except bit 4 of the timer 123 mode register are cleared to
“
0.
”
Set
the interrupt enable bits of timer 1 and timer 2 to disabled (
“
0
”
) before
executing the STP instruction.
Oscillator restarts when an external interrupt is received, but the in-
ternal clock
φ
is not supplied to the CPU until timer 2 underflows.
This allows time for the clock circuit oscillation to stabilize.
(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 before
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 re-
started.
Fig. 36 RC oscillation circuit
Fig. 37 Resonator circuit
C
CIN
Rf
R
d
X
C
I
N
X
C
O
U
T
O
S
C
S
E
L
X
I
N
X
O
U
T
Rosc
X
C
I
N
X
C
O
U
T
O
S
C
S
E
L X
I
N
X
O
U
T
C
I
N
C
OUT
C
C
I
N
C
C
O
U
T
R
f
R
d
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