7480 datasheet(175/337 Pages) RENESAS

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7480 Group and 7481 Group User's Manual

1-158

HARDWARE

1.18 Oscillation Circuit

The 7480 Group and 7481 Group are equipped with a built-in clock generator providing the clock necessary

for operation of the microcomputer. An oscillation circuit is constructed by connecting a ceramic resonator

between the XIN and XOUT pins (Note 1). Also, an external clock can be supplied to the clock generator (Note

2).

The built-in feedback resistor connected between the XIN and XOUT pins allows the user to omit an external

resistor.

Notes 1: For an example of an oscillation circuit using a ceramic resonator, refer to Section 2.6 Oscillation

Circuit. Consult the manufacturer of the resonator for the oscillator start-up stabilization time.

2: Also, for an external clock circuit, refer to Section 2.6 Oscillation Circuit. Use a 50% duty cycle

pulse signal as the external clock input to the XIN pin. At this time, leave the XOUT pin open.

1.18.1 Block Diagram of Clock Generator

The clock generator controls the oscillation circuit. The generated clock (internal clock

φ) is supplied to the

CPU and the peripherals.

Figure 1.18.1 shows the block diagram of the clock generator.

Figure 1.18.1 Block Diagram of Clock Generator

Interrupt disable flag

Interrupt request

WIT

instruction

XIN

XOUT

1/4

1/2

1/4

Reset

STP

instruction

Timer 1

Internal clock

Reset

STP instruction

Clock dividing ratio selection bit

‘0’

‘1’

1.18 Oscillation Circuit

7480 Datasheet(PDF) 175 Page - Renesas Technology Corp