m3819 Renesas Electronics Corporation., m3819 Datasheet - Page 62

• Manufacturer Part Number: m3819
• Description: Mitsubishi 8-bit Single-chip Microcomputer 740 Family / 38000 Series
• Manufacturer: Renesas Electronics Corporation.

CLOCK GENERATING CIRCUIT
The 3819 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 poweron, only the X
oscillation, and X
Frequency Control
Middle-speed mode
The internal clock
set, this mode is selected.
High-speed mode
The internal clock
Low-speed mode
The internal clock
Note : If you switch the mode between middle/high-speed and low-speed,
Low-power dissipation mode
When stopping the main clock X
power dissipation operation starts. To stop the main clock, set the
bit 5 of the CPU mode register to “1”. When the main clock X
restarted, set enough time for oscillation to stabilize by program-
ming.
The low-power dissipation operation 200 A or less (at f(X
kHz) can be realized by reducing the X
duce the X
register to “0”. At reset or when executing the STP instruction, this
bit is set to “1” and strong drivability is selected to help the oscilla-
tion to start.
48
OUT
(X
stabilize both X
quired for the X
after poweron 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
CIN
CIN
and X
–X
COUT
CIN
COUT
CIN
is half the frequency of X
is half the frequency of X
is the frequency of X
IN
CIN
and X
and X
drivability, clear the bit 3 of the CPU mode
and X
). Use the circuit constants in accordance
IN
oscillation to stabilize, especially immediately
) > 3·f(X
COUT
COUT
CIN
oscillations. The sufficient time is re-
IN
pins function as I/O ports.
CIN
.
IN
in the low-speed mode, the low-
).
and X
CIN
IN
–X
IN
oscillation circuit starts
OUT
divided by 8. After re-
COUT
IN
CIN
.
since a feed-back
.
drivability. To re-
IN
IN
) = 32
IN
and
is
Oscillation Control
Stop mode
If the STP instruction is executed, the internal clock
“H” level, and X
and timer 2 is set to “01
put to timer 1, and the output of timer 1 is connected to timer 2.
The bits of the timer 12 mode register are cleared to “0”. Set the
timer 1 and timer 2 interrupt enable bits to disabled (“0”) before ex-
ecuting the STP instruction.
Oscillator restarts at reset or when an external interrupt is re-
ceived, but the internal clock
timer 1 underflows. When using an external resonator, it is neces-
sary for oscillating to stabilize.
Wait mode
If the WIT instruction is executed, the internal clock
“H” level. The states of X
fore executing the WIT instruction. The internal clock 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. 47 Ceramic resonator external circuit
Fig. 48 External clock input circuit
V
V
CC
SS
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
IN
C
and X
X
External oscillation
circuit or pulse
CIN
CIN
X
CIN
MITSUBISHI MICROCOMPUTERS
CIN
X
Open
16
IN
R
COUT
”. Either X
f
X
and X
oscillators stop. Timer 1 is set to “FF
COUT
R
C
d
COUT
CIN
is not supplied to the CPU until
V
V
CC
SS
IN
are the same as the state be-
X
X
External oscillation
circuit
IN
IN
or X
C
IN
3819 Group
Open
CIN
X
X
OUT
OUT
C
divided by 16 is in-
OUT
stops at an
stops at an
16
”