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SH79F3283
32
(continue)
6-5
CLKS [1: 0]
SYSCLK Prescaler Register
00: f
SYS
= f
OSCS
01: f
SYS
= f
OSCS
/2
10: f
SYS
= f
OSCS
/4
11: f
SYS
= f
OSCS
/12
If 32.768kHz oscillator is selected as OSCSCLK, these control bits is invalid.
3
HFON
OSCXCLK On-Off control Register
0: turn off OSCXCLK
1: turn on OSCXCLK
Only when code option OP_OSC is 0011, 0110, 1010, 1101 this bit is valid.
(32.768kHz oscillator/128kHz internal RC is selected, refer to
code option
section for details)
2
FS
Frequency Select Register
0: 32.768kHz/128kHz is selected as OSCSCLK.
1: OSCXCLK is selected as OSCSCLK.
Only when code option OP_OSC is 0011, 0110, 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, 1101, OSCXCLK is
oscillator from XTALX1 input.
(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 setting must be done as the
following steps:
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 setting must be done as the following steps:
a. Clear FS to select 32.768kHZ/128k as OSCSCLK.
b. Add one NOP
c. Clear HFON (reduce power consumption)
d. Add four NOPs.