SM5M2 datasheet(13/28 Pages) SHARP

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SM5M2

- 13 -

OSCIN

OSC

OSCOUT

OSCIN-OSCOUT : Crystal oscillation

(32.768 kHz)

CK2

OSC

CK1

CK1-CK2 : CR oscillation

(70 kHz)

MPX.

fSYS

fSYS = 17.5 kHz or 35 kHz

f14

1 Hz

2 Hz

fC = 1 Hz or 2 Hz

Determined by

mask option

4 kHz 2 kHz

256 Hz

RF2

Divider

Fig. 8

System Clock Generator and Divider

Either of the system clock frequencies 35 kHz or

17.5 kHz ( in case of CR oscillation) can be

selected by the RF2 flag (See Table 2). The 17.5

kHz clock has slower command execution speed,

but uses less power for the same function.

The system clock is initialized to 35 kHz after

hardware reset operation.

The Table 2 shows the relationship between the

contents of RF2 flag for OSC resonator and the

generated frequency, fSYS.

Table 2

OSC Resonator and Frequency fSYS

FOR OSC RESONATOR

CONTENTS OF RF2 FLAG

GENERATED FREQUENCY fSYS

70 kHz CR oscillation

35 kHz

17.5 kHz

32.768 kHz crystal

16.384 kHz

8.192 kHz

System Clock Generator and Dividers

The main oscillation frequency (CR oscillator) which

is input through CK1 is divided into 2 or 4 to

generate the system clock fSYS (Fig. 8).

System clock fSYS determines the execution

instruction cycle so that the system clock period is

the same as the instruction cycle.

However, the instruction execution cycle of two-

word

instruction

twice

that

one-word

instructions.

Use of a CR oscillating element or a crystal

oscillating element for the oscillator circuit is

determined by the mask option. The crystal

oscillator which is input through "OSCIN-OSCOUT"

can be used as both real time clock and display

signal of LCD. On the final stage of the divider, fc

can be set 1 Hz or 2 Hz ( in case of 32 kHz crystal

oscillation) depending on the mask option.

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