r5f21346mnfp Renesas Electronics Corporation., r5f21346mnfp Datasheet - Page 157

• Manufacturer Part Number: r5f21346mnfp
• Description: Single-chip Mcus Incorporates The R8c Cpu Core
• Manufacturer: Renesas Electronics Corporation.

R8C/34M Group
R01UH0131EJ0100 Rev.1.00
Jun 21, 2011
9.5
Figure 9.4
The XCIN clock is supplied by the XCIN clock oscillation circuit. This clock is used as the clock source for the
CPU and peripheral function clocks. The XCIN clock oscillation circuit is configured by connecting a resonator
between the XCIN and XCOUT pins. The XCIN clock oscillation circuit includes an on-chip a feedback resistor,
which is disconnected from the oscillation circuit in stop mode in order to reduce the amount of power consumed
by the chip. The XCIN clock oscillation circuit may also be configured by feeding an externally generated clock to
the XCIN pin.
Figure 9.4 shows Examples of XCIN Clock Connection Circuits.
During and after a reset, the XCIN clock stops.
After setting the XCSEL bit in the PINSR register to 1 (XCIN connected to P4_3, XCOUT connected to P4_4) and
the CM04 bit in the CM0 register to 1 (XCIN-XCOUT pin), the XCIN clock starts oscillating when the CM03 bit
in the CM0 register is set to 0 (XCIN clock oscillates). After the XCIN clock oscillation stabilizes, the XCIN clock
is used as the CPU clock source when the CM07 bit in the CM0 register is set to 1 (XCIN clock). To input an
externally generated clock to the XCIN pin, also set the CM04 bit in the CM0 register to 1 (XCIN-XCOUT pin).
Leave the XCOUT pin open at this time.
This MCU 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 stop. Refer to 9.7 Power Control for details.
Note:
1. To input an externally generated clock from the XCIN pin, set the CM03 bit in the CM0 register to 1 (XCIN
• When CM03 bit in CM0 register is set
clock stops) and the CM12 bit in the CM1 register to 1 (on-chip feedback resistor disabled).
to 0 (XCIN clock oscillates) and CM04
bit is set to 1 (XCIN-XCOUT pin)
XCIN Clock
External crystal oscillator circuit
Note:
XCIN
1. Insert a damping resistor and feedback resistor if required. The resistance will vary depending on
(on-chip feedback resistor)
If the oscillator
the oscillator and the oscillation drive capacity setting. Use the value recommended by the oscillator
manufacturer.
insert a feedback resistor between XCIN and XCOUT following the instructions.
Examples of XCIN Clock Connection Circuits
(1)
CIN
MCU
Rf
(1)
manufacturer's datasheet specifies that a feedback resistor be added to the chip externally,
XCOUT
Rd
COUT
(1)
• When CM03 bit in CM0 register is set
to 1 (XCIN clock stops) and CM04 bit
is set to 1 (XCIN-XCOUT pin), and
CM12 bit in CM1 register is set to 1
(on-chip feedback resistor disabled)
VSS
VCC
Externally generated clock
XCIN
External clock input circuit
(on-chip feedback resistor)
MCU
9. Clock Generation Circuit
XCOUT
Open
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