S�Stem Ope�Ation Modes - Holtek BS83B24C Manual

BS83B24C/BS83C40C
Touch Flash MCU
System Operation Modes
There are six different modes of operation for the microcontroller, each one with its own
special characteristics and which can be chosen according to the specific performance and
power requirements of the application. There are two modes allowing normal operation of the
microcontroller, the FAST Mode and SLOW Mode. The remaining four modes, the SLEEP, IDLE0,
IDLE1 and IDLE2 Mode are used when the microcontroller CPU is switched off to conserve power.
Operation
CPU
Mode
�AST On
SLOW On
IDLE0 Off
IDLE1 Off
IDLE� Off
SLEEP Off
Notes: 1. The f clock will be switched on or off by configuring the corresponding oscillator enable
H
bit in the SLOW mode.
2. The f
LIRC
FAST Mode
As the name suggests this is one of the main operating modes where the microcontroller has all of
its functions operational and where the system clock is provided by the high speed oscillator. This
mode operates allowing the microcontroller to operate normally with a clock source will come from
the HIRC oscillator. The high speed oscillator will however first be divided by a ratio ranging from
1 to 64, the actual ratio being selected by the CKS2~CKS0 bits in the SCC register. Although a high
speed oscillator is used, running the microcontroller at a divided clock ratio reduces the operating
current.
SLOW Mode
This is also a mode where the microcontroller operates normally although now with a slower speed
clock source. The clock source used will be from f
LIRC oscillator, which is selected via the software control bit FSS in the SCC register.
SLEEP Mode
The SLEEP Mode is entered when an HALT instruction is executed and when the FHIDEN and
FSIDEN bit are low. In the SLEEP mode the CPU will be stopped, and the f
will be stopped too. However the f
enabled.
IDLE0 Mode
The IDLE0 Mode is entered when a HALT instruction is executed and when the FHIDEN bit in
the SCC register is low and the FSIDEN bit in the SCC register is high. In the IDLE0 Mode the
CPU will be switched off but the low speed oscillator will be turned on to drive some peripheral
functions.
Rev. 1.00
Register Setting
FHIDEN FSIDEN CKS2~CKS0
x x 000~110
x x 111
000~110
0 1
111
1 1 xxx
000~110
1 0
111
0 0 xxx
clock is always on as the WDT function is always enabled.
clock will continue to operate as the WDT function is always
LIRC
4�
f f
SYS H
f ~f /64 On
H H
(1)
f On/Off
SUB
Off
Off
On
On On
On
On
Off
Off Off
. The f clock is derived from the LXT or
SUB SUB
clock to peripheral
SUB
�e���a�� 0�� �01�
f f
SUB LIRC
On On
On On
On On
On On
Off On
(�)
Off On
"x": Don't ca�e