Contro� Register - Holtek HT68F Series Manual

• IDLE0 Mode
The IDLE0 Mode is entered when a HALT instruction is executed and when the IDLEN bit in
the SMOD register is high and the FSYSON bit in the WDTC register is low. In the IDLE0 Mode
the system oscillator will be inhibited from driving the CPU but some peripheral functions will
remain operational such as the Watchdog Timer, TMs and SIM. In the IDLE0 Mode, the system
oscillator will be stopped. In the IDLE0 Mode the Watchdog Timer clock, f
off depending upon the f
the source comes from f
• IDLE1 Mode
The IDLE1 Mode is entered when an HALT instruction is executed and when the IDLEN bit
in the SMOD register is high and the FSYSON bit in the WDTC register is high. In the IDLE1
Mode the system oscillator will be inhibited from driving the CPU but may continue to provide a
clock source to keep some peripheral functions operational such as the Watchdog Timer, TMs and
SIM. In the IDLE1 Mode, the system oscillator will continue to run, and this system oscillator
may be high speed or low speed system oscillator. In the IDLE1 Mode the Watchdog Timer
clock, f , will be on. If the source is f
S
from f then f
SUB
Control Register
A single register, SMOD, is used for overall control of the internal clocks within the device.
SMOD Register
Bit 7
Name CKS2
R/W R/W
POR 0
CKS2~CKS0: The system clock selection when HLCLK is "0"
Bit 7~5
000: f
001: f
010: f
011: f
100: f
101: f
110: f
111: f
These three bits are used to select which clock is used as the system clock source. In
addition to the system clock source, which can be either the LXT or LIRC, a divided
version of the high speed system oscillator can also be chosen as the system clock
source.
Bit 4 FSTEN: Fast Wake-up Control (only for HXT)
0: Disable
1: Enable
This is the Fast Wake-up Control bit which determines if the f
initially used after the device wakes up. When the bit is high, the f
be used as a temporary system clock to provide a faster wake up time as the f
is available.
Rev. 2.10
HT68F20/HT68F30/HT68F40/HT68F50/HT68F60
HT68FU30/HT68FU40/HT68FU50/HT68FU60
Enhanced I/O Flash Type 8-Bit MCU with EEPROM
clock source. If the source is f
S
then f will be on.
SUB S
/4 then the f
SYS
will be on.
S
6 5 4
CKS1 CKS0 FSTEN
R/W R/W R/W
0 0 0
(f or f )
L LXT LIRC
(f or f )
L LXT LIRC
/64
H
/32
H
/16
H
/8
H
/4
H
/2
H
58
, will either be on or
S
/4 then the f clock will be off, and if
SYS S
clock will be on, and if the source comes
S
3 2 1
LTO HTO IDLEN
R R R/W
0 0 1
clock source is
SUB
clock source can
SUB
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0
HLCLK
R/W
1
clock
SUB