34
MITSUBISHI MICROCOMPUTERS
4570 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
CLOCK CONTROL
The clock control circuit consists of the following circuits.
G
Clock generating circuit
G
Control circuit to stop the clock oscillation
G
System clock selection circuit
G
Instruction clock generating circuit
G
Control circuit to return from the RAM back-up mode
Fig. 32 Clock control circuit structure
Fig. 33 Ceramic resonator external circuit
Clock signal f(X
IN
) is obtained by externally connecting a ceramic
resonator. Connect this external circuit to pins X
IN
and X
OUT
at
the shortest distance. A feedback resistor is built-in between pins
X
IN
and X
OUT
.
ROM ORDERING METHOD
Please submit the information described below when ordering
Mask ROM.
(1) M34570M4-XXXFP Mask ROM Order Confirmation Form,
M34570M8-XXXFP Mask ROM Order Confirmation Form, or
M34570MD-XXXFP Mask ROM Order Confirmation Form
..............................................................................................1
(2) Data to be written into mask ROM.......................... EPROM
(three sets containing the identical data)
(3) Mark Specification Form .................................................... 1
The wait time control circuit is automatically used to generate the time required to stabilize the
f(X
IN
) oscillation.
Internal clock
generating circuit
(devided by 3)
Insturuction clock
I1
2
“H”
level
0
“L” level
1
MR
3
1
0
RESET
Key-on wakeup control register
Falling detected
Port P4
0
Port P4
1
Port P4
2
Port P4
3
Multi-
plexer
K0
0
,K0
1
,K0
2
,K0
3
Counter
Wait time control
circuit (Note)
Software
start signal
Frequency dividing
circuit
(divided by 4)
R
S
Q
POF instruction
X
IN
X
OUT
P2
1
/INT
Oscillation
circuit
Ports P0, P1
System clock
Note:
M34570
X
IN
X
OUT
Rd
C
IN
C
OUT
Externally connect a
damping resistor Rd
depending on the
oscillation frequency.
(A feedback resistor is
built-in.)
Use the resonator
manufacturer’s
recommended value
because constants such
as capacitance depend
on the resonator.
Note: