System Operation Modes
There are five 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 NORMAL Mode and SLOW Mode. The remaining three modes, the SLEEP,
IDLE0 and IDLE1 Mode are used when the microcontroller CPU is switched off to conserve power.
Operation
Mode
Description
CPU
f
SYS
f
LIRC
f
TBC
NORMAL Mode
On
f
H
~ f
H
/64
On
On
SLOW Mode
On
f
L
On
On
IDLE0 Mode
Off
Off
On
On
IDLE1 Mode
Off
On
On
On
SLEEP Mode
Off
Off
On
Off
·
NORMAL 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. 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 and HLCLK bits in the SMOD 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 the slow speed
clock source. Running the microcontroller in this mode allows it to run with much lower operating
currents. In the SLOW Mode, the high speed clock is off.
·
SLEEP Mode
The SLEEP Mode is entered when a HALT instruction is executed and when the IDLEN bit in the
SMOD register is low. In the SLEEP mode the CPU will be stopped however as the f
LIRC
oscillator
continues to run the Watchdog Timer will continue to operate.
·
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 the system oscillator will be stopped and will therefore be inhibited from driving
the CPU.
·
IDLE1 Mode
The IDLE1 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 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. In the IDLE1 Mode, the system oscillator will
continue to run, and this system oscillator may be the high speed or low speed system oscillator.
Rev. 1.50
40
April 28, 2020
BS83B08-3/B12-3/B16-3/B16G-3/C24-3
8-Bit Touch Key Flash MCU