m37702s1afp Mitsumi Electronics, Corp., m37702s1afp Datasheet - Page 44

• Manufacturer Part Number: m37702s1afp
• Description: Single-chip 16-bit Cmos Microcomputer
• Manufacturer: Mitsumi Electronics, Corp.

CLOCK GENERATING CIRCUIT
Figure 55 shows a block diagram of the clock generator.
When an STP instruction is executed, the internal clock
oscillating at “L” level. At the same time, FFF
dog timer and the watchdog timer input connection is forced to f
This connection is broken and connected to the input determined
by the watchdog timer frequency selection flag when the most sig-
nificant bit of the watchdog timer is cleared or reset.
Oscillation resumes when an interrupt is received, but the internal
clock
watchdog timer is cleared. This is to avoid the unstable interval at
the start of oscillation when using a ceramic resonator.
When a WIT instruction is executed, the internal clock
“L” level, but the oscillator does not stop. The clock is restarted
when an interrupt is received. Instructions can be executed imme-
diately because the oscillator is not stopped.
The stop or wait state is released when an interrupt is received or
when reset is issued. Therefore, interrupts must be enabled be-
fore executing a STP or WIT instruction.
Figure 56 shows a circuit example using a ceramic (or quartz crys-
tal) resonator. Use the manufacture’s recommended values for
constants such as capacitance which differ for each resonator.
Figure 57 shows an example of using an external clock signal.
Fig. 55 Block diagram of a clock generator
44
remains at “L” level until the most significant bit of the
Interrupt request
STP instruction
X
IN
S
R
X
Q
OUT
WIT instruction
1/2
16
is written to watch-
f
2
M37702M2AXXXFP, M37702M2BXXXFP
1/8
stops at
S
R
stops
Internal clock
32
Q
f
16
.
1/2
Fig. 56 Circuit using a ceramic resonator
Fig. 57 External clock input circuit
M37702S1AFP, M37702S1BFP
f
32
External clock source
Vcc
Vss
1/2
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Q
29
29
X
X
S
R
IN
IN
f
64
MITSUBISHI MICROCOMPUTERS
M37702M2AXXXFP
M37702M2AXXXFP
1/8
STP instruction
1M
Reset
f
512
Watchdog
timer
X
Open
X
OUT
OUT
30
Rd
30