4559 datasheet(62/148 Pages) RENESAS

62 / 148 page

Rev.1.04

Aug 23, 2007

Page 62 of 146

REJ03B0188-0104

4559 Group

(1) On-chip oscillator operation

After system is released from reset, the MCU starts operation by

the clock output from the on-chip oscillator which is the internal

oscillator.

The clock frequency of the on-chip oscillator depends on the

supply voltage and the operation temperature range.

Be careful that variable frequencies when designing application

products.

(2) Main clock generating circuit (f(XIN))

When the MCU operates by the ceramic resonator or the RC

oscillator as the main clock (f(XIN)).

After system is released from reset, the ceramic oscillation is

valid for main clock.

The ceramic oscillation is invalid and the RC oscillation circuit is

valid with the CRCK instruction.

The CRCK instruction can be executed only once.

Execute the CRCK instruction in the initial setting routine

(executing it in address 0 in page 0 is recommended).

When the main clock (f(XIN)) is not used, connect XIN pin to VSS

and leave XOUT pin open, and do not execute the CRCK

instruction (Figure 61).

(3) Ceramic resonator

When the ceramic resonator is used as the main clock (f(XIN)),

connect the ceramic resonator and the external circuit to pins XIN

and XOUT at the shortest distance.

A feedback resistor is built in between pins XIN and XOUT

(Figure 62). Do not execute the CRCK instruction in program.

(4) RC oscillation

When the RC oscillation is used as the main clock (f(XIN)),

connect the XIN pin to the external circuit of resistor R and the

capacitor C at the shortest distance and leave XOUT pin open.

Then, execute the CRCK instruction (Figure 63).

To select RC oscillation as the system clock, select the main

clock (f(XIN) as the system clock by bits 0 and 1 of the clock

control register MR.

The frequency is affected by a capacitor, a resistor and a

microcomputer. So, set the constants within the range of the

frequency limits.

Fig 60. Switch to ceramic resonance/RC oscillation

Fig 61. Handling of XIN and XOUT when operating on-

chip oscillator

Fig 62. Ceramic resonator external circuit

Fig 63. External RC oscillation circuit

Reset

CRCK

• Ceramic resonator circuit valid

• RC oscillation circuit invalid

Main clock (f(XIN))

• Ceramic resonator circuit invalid

• RC oscillation circuit valid

Do not use the CRCK instruction in program.

4559

XIN

XOUT

4559

XIN

XOUT

CIN

COUT

Do not execute the CRCK instruction in program.

Note: Externally connect a damping resistor Rd

depending on the oscillation frequency.

(A feedback resistor is built-in.)

Use the resonator manufacturer’s recommended

value because constants such as capacitance

depend on the resonator.

4559

XIN

XOUT

Execute the CRCK

instruction in program.

4559 Datasheet(PDF) 62 Page - Renesas Technology Corp

4559 Datasheet(HTML) 62 Page - Renesas Technology Corp

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