r5f21368sdfp Renesas Electronics Corporation., r5f21368sdfp Datasheet - Page 127

• Manufacturer Part Number: r5f21368sdfp
• Description: Renesas Mcu R8c Family / R8c/3xt-a Series
• Manufacturer: Renesas Electronics Corporation.

Under development
R8C/36T-A Group
R01UH0240EJ0001 Rev.0.01
Apr 28, 2011
9.5
Figure 9.4
Note:
The XIN clock is supplied by the XIN clock oscillation circuit. This clock is used as the clock source for the CPU
clock and the peripheral function clock. The XCIN clock oscillation circuit is configured by connecting an
oscillator between pins XCIN and XCOUT. The XCIN clock oscillation circuit includes an on-chip feedback
resistor, which is disconnected from the oscillation circuit in stop mode to reduce power consumption. The XCIN
clock oscillation circuit also allows an externally generated clock to be input to the XCIN pin.
Figure 9.4 shows Connection Examples of XCIN Clock Oscillation Circuit.
The XCIN clock is stopped during and after a reset.
After the XCSEL bit in the PINSR register is set to 1 (XCIN is connected to P4_3 and XCOUT is connected to
P4_4) and the CM04 bit in the CM0 register is set to 1 (Xtal used), when the CM03 bit in the CM0 register is set to
0 (XCIN clock oscillates), the XCIN clock starts oscillating. After the XIN clock oscillation stabilizes, when bits
CM42 to CM40 in the CM4 register are set to 010b (XCIN clock), the XCIN clock is used as the clock source for
the CPU. When inputting an externally generated clock to the XCIN pin, set the CM04 bit to 0 (external clock input
from XCIN). Leave the XCOUT pin open at this time.
The R8C/36T-A Group has an on-chip feedback resistor, which can be disabled/enabled by the CM12 bit in the
CM1 register.
In stop mode, all clocks including the XCIN clock are stopped. For details, refer to 10. Power Control.
External ceramic resonator connected circuit
1. Insert a damping resistor or feedback resistor if necessary. The resistance will vary depending on the
•
oscillator and the oscillation drive capacity. Use the values recommended by the oscillator manufacturer.
When the oscillation drive capacity is set to low, check that the oscillation is stable even in that state. If the
manufacturer specifies that a feedback resistor be added to the chip externally, insert a feedback resistor
between XCIN and XCOUT following the instructions.
When XCSEL bit in PINSR register is
XCIN Clock
1 (XCIN is connected to P4_3 and
XCOUT is connected to P4_4), CM03
bit in CM0 register is 0 (oscillates),
and CM04 bit in CM0 register is 1
(Xtal used)
XCIN
(on-chip feedback resistor)
Preliminary document
Specifications in this document are tentative and subject to change.
Connection Examples of XCIN Clock Oscillation Circuit
CIN
MCU
Rf
(1)
XCOUT
Rd
COUT
(1)
•
When XCSEL bit in PINSR register is
1 (XCIN is connected to P4_3 and
XCOUT is connected to P4_4), CM03
bit in CM0 register is 0 (oscillates),
and CM04 bit in CM0 register is 0
(external clock input from XCIN)
VCC
VSS
Externally generated clock
XCIN
(on-chip feedback resistor)
External clock input circuit
MCU
9. Clock Generation Circuit
XCOUT
Open
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