M38203M4 Datasheet, PDF (276/344 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.11 Oscillation circuit
2.11 Oscillation circuit
2.11.1 Oscillation circuit
Two oscillation circuits are included to obtain clocks required for operations.
• XIN–XOUT oscillation circuit............Main clock (XIN input) oscillation circuit
• XCIN–XCOUT oscillation circuit........Sub-clock (XCIN input) oscillation circuit
A clock^V1 obtained by dividing the frequency input to the clock input pins XIN or XCIN is an internal clock
φ. The internal clock φ is used as a standard for operations.
V1: The internal clock φ varies with modes.
•High-speed mode ........Frequency input to the XIN pin/2
•Middle-speed mode .....Frequency input to the XIN pin/8
•Low-speed mode .........Frequency input to the XCIN pin/2
(1) Oscillation circuit using ceramic resonators
Figure 2.11.1 shows an oscillation circuit example using ceramic resonators. As shown in the figure,
an oscillation circuit can be formed by connecting a ceramic resonator or a quartz-crystal oscillator
between the pins XIN and the XOUT and between the pins XCIN and XCOUT. As the XIN–XOUT oscil-
lation circuit includes a feedback resistor, an external resistor is omissible.
As the XCIN–XCOUT oscillation circuit does not include any feedback resistor, connect a feedback
resistor externally.
Regarding circuit constants for Rf, Rd, CIN, COUT, CCIN and CCOUT, ask the resonator manufacturer
for information, and set the values recommended by the resonator manufacturer.
XCIN
28
3820 group
XCOUT
Rf
29
XIN
30
Rd
CCIN
CCOUT CIN
XOUT
31
COUT
Fig. 2.11.1 Oscillation circuit example using ceramic resonators
2–190
3820 GROUP USER’S MANUAL