M38867E8AHP MITSUBISHI [Mitsubishi Electric Semiconductor], M38867E8AHP Datasheet - Page 58

• Manufacturer Part Number: M38867E8AHP
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER??
• Manufacturer: MITSUBISHI [Mitsubishi Electric Semiconductor]

CLOCK GENERATING CIRCUIT
The 3886 group has two built-in oscillation circuits. An oscillation
circuit can be formed by connecting a resonator between X
X
with the resonator manufacturer’s recommended values. No exter-
nal resistor is needed between X
resistor exists on-chip. However, an external feed-back resistor is
needed between X
Immediately after power on, only the X
oscillating, and X
Frequency Control
(1) Middle-speed mode
The internal clock
set, this mode is selected.
(2) High-speed mode
The internal clock
(3) Low-speed mode
The internal clock
If you switch the mode between middle/high-speed and low-
speed, stabilize both X
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 middle/high-speed and low-speed, set the fre-
quency on condition that f(X
(4) Low power dissipation mode
The low power consumption operation can be realized by stopping
the main clock X
bit 5 of the CPU mode register to “1.” When the main clock X
restarted (by setting the main clock stop bit to “0”), set sufficient
time for oscillation to stabilize.
Oscillation Control
(1) Stop mode
If the STP instruction is executed, the internal clock
“H” level, and X
stabilizing time set after STP instruction released bit is “0,” the
prescaler 12 is set to “FF
oscillation stabilizing time set after STP instruction released bit is
“1,” set the sufficient time for oscillation of used oscillator to stabi-
lize since nothing is set to the prescaler 12 and timer 1.
Either X
count source, and the output of the prescaler 12 is connected to
timer 1. Set the timer 1 interrupt enable bit to disabled (“0”) before
executing the STP instruction. Oscillator restarts when an external
interrupt is received, but the internal clock
CPU (remains at “H”) until timer 1 underflows. The internal clock
is supplied for the first time, when timer 1 underflows. Therefore
make sure not to set the timer 1 interrupt request bit to “1” before
the STP instruction stops the oscillator. When the oscillator is re-
started by reset, apply “L” level to the RESET pin until the
oscillation is stable since a wait time will not be generated.
58
OUT
Note
(X
CIN
IN
or X
and X
CIN
IN
IN
CIN
COUT
CIN
and X
in low-speed mode. To stop the main clock, set
divided by 16 is input to the prescaler 12 as
is half the frequency of X
is half the frequency of X
is the frequency of X
and X
and X
IN
). Use the circuit constants in accordance
CIN
16
and X
COUT
” and timer 1 is set to “01
COUT
IN
oscillators stop. When the oscillation
) > 3f(X
CIN
pins function as I/O ports.
.
IN
oscillations. The sufficient time
and X
CIN
IN
).
IN
oscillation circuit starts
OUT
divided by 8. After re-
is not supplied to the
IN
CIN
.
since a feed-back
.
16
.” When the
stops at an
IN
IN
and
is
(2) Wait mode
If the WIT instruction is executed, the internal clock
“H” level, but the oscillator does not stop. The internal clock
starts 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. 58 Ceramic resonator circuit
Fig. 59 External clock input circuit
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
V
V
E x t e r n a l o s c i l l a t i o n
C C
S S
X
X
c i r c u i t
CIN
C I N
C
MITSUBISHI MICROCOMPUTERS
Rf
CIN
X
X
O p e n
COUT
C O U T
Rd
C
COUT
E x t e r n a l o s c i l l a t i o n
X
V
V
IN
C C
S S
C
X
c i r c u i t
IN
I N
X
3886 Group
OUT
C
O p e n
X
OUT
O U T
stops at an
re-