SH79F6488PSLASH080PR datasheet(35/152 Pages) SINOWEALTH

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SH79F6488/SH79F6489

7.5.3 Description

SH79F6488/SH79F6489 has four oscillator types: 32.768kHz crystal oscillator, crystal/ceramic oscillator, PLL and internal RC

(12MHz), which is selected by code option OP_OSC (Refer to code option section for details). SH79F6488/SH79F6489 have 4

Oscillator pin (XTAL1, XTAL2, XTALX1, XTALX2) and can generates one or two clock sources from four oscillator types. It is

selected by code option OP_OSC (Refer to code option section for details). The oscillator generates the basic clock pulse that

provides the system clock to supply CPU and on-chip peripherals.

When OSC1CLK is used as OSCSCLK (FS = 0), and the system enters Power-down mode, OSC1CLK and OSC2CLK will shut

down. If base timer or LCD worked, OSC1CLK will not shut down, but OSC2CLK will.

When OSC2CLK is used as OSCSCLK (FS = 0), and the system enters Power-down mode, OSC2CLK will shut down.

OSC1CLK will work for on-chip peripherals (Timer3,base timer and so on)

Internal 12MHz RC support hardware or software adjustion. When CLKRCEN = 0, internal RC is adjusted by hardware.

CLKRCEN = 1, internal RC is adjusted by software, by modifying the CLKRC0 register values to adjust the RC frequency.

CLKRC1 is the initial adjustion value. When adjust the RC oscillation frequency deviation is larger, users can get correction

initial value by read-only register CLKRC1.

7.5.4 Registers

Table 7.15 System Clock Control Register

B2H

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

CLKCON

32k_SPDUP

CLKS1

CLKS0

SCMIF

OSC2ON

R/W

Reset Value

(POR/WDT/LVR/PIN)

Bit Number

Bit Mnemonic

Description

32k_SPDUP

32.768kHz oscillator speed up mode control bit

0: 32.768kHz oscillator normal mode, cleared by software.

1: 32.768kHz oscillator speed up mode, set by hardware or software.

This control bit is set by hardware automatically in all kinds of RESET such as

Power on reset, watch dog reset etc. to speed up the 32.768kHz Oscillator

oscillating, shorten the 32.768kHz oscillator start-oscillating time.

And this bit also can be set or cleared by software if necessary. Such as set before

entering Power-down mode and cleared when Power-down mode wakes up.

It should be noticed that turning off 32.768kHz oscillator speed up (clear this bit)

could reduce the system power consumption.

Only when code option OP_OSC is 1010 or 1101, this bit is valid. (32.768kHz

oscillator is selected, Refer to code option section for details)

6-5

CLKS[1:0]

SYSCLK Prescaler Register

00: fSYS = fOSCS

01: fSYS = fOSCS/2

10: fSYS = fOSCS/4

11: fSYS = fOSCS/12

If 32.768kHz oscillator is selected as OSCSCLK, these control bits is invalid.

OSC2ON

OSC2CLK On control Register

0: Cleared to turn off OSC2CLK

1: Set to turn on OSC2CLK

Frequency Select Register

0: OSC1CLK is selected as OSCSCLK

1: OSC2CLK is selected as OSCSCLK

SH79F6488P/080PR Datasheet(PDF) 35 Page - SINOWEALTH Electronic Ltd

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