M37160M8 Datasheet, PDF (85/131 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

M37160M8/MA/MF-XXXSP/FP,M37160EFSP/FP
8.13 CLOCK GENERATING CIRCUIT
This microcomputer contains two internal oscillator circuits, one os-
cillator circuit for the main clock and XCIN-XCOUT for the subclock.
The main clock and OSD clock are generated based on the refer-
ence clock from the FSCIN pin. The subclock can be obtained by
connecting a resonator between XCIN and XCOUT to configure an
oscillator circuit. Because the resistance-capacitance time constants
vary with each resonator, be sure to use the value recommended by
the resonator manufacturer. The subclock can also be supplied di-
rectly from the FSCIN pin. For the FILT pin used to generate the
main clock, insert the filter shown in Figure 8.13.1. Because no resis-
tors are included between XCIN and XCOUT, please insert feedback
resistors external to the chip.
After reset, the internal clock f is derived from f(XIN) by dividing it by 2.
Immediately after power-on, the XIN and XCIN clocks both start oscil-
lating. To select low-speed mode for the internal clock f, set the CPU
Mode Register bit 7 to 1.
When operate system clock generating circuit at using standard clock
from FSCIN, set bit 0 of clock control register 1 (address 00CD16) to
“0.”
Microcomputer
XCIN XCOUT FSCIN
FILT
Rf
CCIN
0.01 µF
Rd
External input
CCOUT
0.01 µF
C1
Fig.8.13.1 Ceramic Resonator Circuit Example
XCIN/XCOUT
FSCIN
(4.43MHz)
32kHz of
oscillation circuits
Generating circuit
system clock
"1"
Sub clock
f(XCIN)
"0" ^{CC2 address 021116 bit 2}
"1"
Main clock
f(XIN)
Inside system
"0" ^{clock of switch circuit}
Clock for OSD
f(OSC)
CM address 00FB16 bit 7(CM7)
f (Φ)
f(XIN) = 8.86 MHz f(OSC) = 26.58 MHz at 4.43 MHz oscillation frequency
Fig.8.13.2 clock generation circuit
Rev.1.01 2003.11.13 page 85 of 130