
R8C/36T-A Group
9. Clock Generation Circuit
Under development Preliminary document
Specifications in this document are tentative and subject to change.
R01UH0240EJ0010 Rev.0.10
Page 82 of 728
Aug 05, 2011
9.
Clock Generation Circuit
9.1
Overview
The following five circuits are included in the clock generation circuit:
XIN clock oscillation circuit
XCIN clock oscillation circuit
Low-speed on-chip oscillator
High-speed on-chip oscillator
Low-speed on-chip oscillator for the watchdog timer
Notes:
1. When the on-chip oscillator clock is used as the CPU clock without using the XIN clock oscillation circuit, these pins can be used as P4_6 and
P4_7.
2. When the XIN clock oscillation circuit or the on-chip oscillator clock is used as the CPU clock without using the XCIN clock oscillation circuit,
these pins can be used as P4_3 and P4_4.
3. When inputting an external clock, set the CM05 bit in the CM0 register to 0 (oscillates), the CM07 bit in the CM0 register to 1 (XIN clock is
supplied by external clock input to XOUT pin), and the CM13 bit in the CM1 register to 1 (XIN-XOUT pin).
4. When the high-speed on-chip oscillator is used as the CPU clock source, the frequency will be a maximum of 20 MHz by setting the divider.
5. This applies when the CSPROINI bit in the OFS register is 1 (count source protection mode disabled after reset).
6. This applies when the CSPROINI bit is 0 (count source protection mode enabled after reset).
Table 9.1
Clock Generation Circuit Specifications
Item
XIN Clock Oscillation
Circuit
XCIN Clock Oscillation
Circuit
Oscillators
Low-Speed On-Chip
Oscillator for
Watchdog Timer
High-Speed
On-Chip Oscillator
Low-Speed
On-Chip Oscillator
Applications
CPU clock source
Peripheral function
clock source
CPU clock source
Peripheral function
clock source
CPU clock source
Peripheral function clock source
CPU and peripheral function clock sources
when the XIN clock oscillation stops.
Watchdog timer
clock source
Clock frequency
0 to 20 MHz
32.768 kHz
Approx.125 kHz
Approx. 125 kHz
Connectable oscillator
Ceramic resonator
Crystal oscillator
——
Oscillator connect pins
—
Oscillation start and stop
Usable
State after reset
Stopped
Others
An externally
generated clock can
An externally
generated clock can
be input.
A feedback resistor
Rf is included
(connected or not
connected can be
selected).
——