SH79F166APSLASH044PR datasheet(29/113 Pages) SINOWEALTH

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SH79F166A

7.5.4 Register

Table 7.13 System Clock Control Register

B2H, Bank0

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

CLKCON

32k_SPDUP

CLKS1

CLKS0

SCMIF

HFON

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.

HFON

OSCXCLK On control Register

0: Cleared to turn off OSCXCLK

1: Set to turn on OSCXCLK

Only when code option OP_OSC is 0010，0011，0101，1010,1101. this bit is valid.

(32.768kHz oscillator/128kHz internal RC is selected, Refer to code option

section for details)

Frequency Select Register

0: 32.768kHz/128kHz is selected as OSCSCLK

1: OSCXCLK is selected as OSCSCLK

Only when code option OP_OSC is 0010，0011，0101，1010,1101. this bit is valid.

(32.768kHz oscillator/128kHz internal RC is selected, Refer to code option

section)

Note:

1. If code option OP_OSC is 0011, 1010, OSCXCLK is Internal 12M RC; if code option OP_OSC is 0110 or 1101, OSCXCLK is

crystal or ceramic at XTALX.

2. HFON and FS is valid only when code option OP_OSC is 0011, 0110, 1010, 1101.

3. When OSCXCLK is used as OSCSCLK (that is HFON = 1 and FS = 1), HFON is can’t be cleared by software.

4. When OSCSCLK changed from 32.768kHz/128kHz to OSCXCLK, if OSCXCLK is off, the steps below must be done in

sequence:

a. Set HFON = 1 to turn on the OSCXCLK

b. Wait at least Oscillator Warm-up timer (Refer to Warm-up Timer section for details)

c. Set FS = 1 to select OSCXCLK as OSCSCLK

5. When OSCSCLK changed from OSCXCLK to 32.768kHz/128kHz, the steps below must be done in sequence:

a. Clear FS to turn off the OSCXCLK

b. Add one nop

c. Clear HFON

SH79F166AP/044PR Datasheet(PDF) 29 Page - SINOWEALTH Electronic Ltd

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