Operating Mode Switching
The device can switch between operating modes dynamically allowing the user to select the best
performance/power ratio for the present task in hand. In this way microcontroller operations that do
not require high performance can be executed using slower clocks thus requiring less operating current
and prolonging battery life in portable applications.
In simple terms, Mode Switching between the NORMAL Mode and SLOW Mode is executed using
the HLCLK bit and CKS2~CKS0 bits in the SMOD register while Mode Switching from the
NORMAL/SLOW Modes to the SLEEP/IDLE Modes is executed via the HALT instruction. When a
HALT instruction is executed, whether the device enters the IDLE Mode or the SLEEP Mode is
determined by the condition of the IDLEN bit in the SMOD register and FSYSON in the WDTC
register.
When the HLCLK bit switches to a low level, which implies that clock source is switched from the
high speed clock source, f
HIRC
, to the clock source, f
HIRC
/2~f
HIRC
/64 or f
LIRC
. If the clock is from f
HIRC
, the
high speed clock source will stop running to conserve power. When this happens it must be noted that
the f
HIRC
/16 and f
HIRC
/64 internal clock sources will also stop running. The accompanying flowchart
shows what happens when the device moves between the various operating modes.
BS83B08-3/B12-3/B16-3/B16G-3/C24-3
8-Bit Touch Key Flash MCU
Rev. 1.50
41
April 28, 2020
N O R M A L
f
S Y S
= f
H
~ f
H
/ 6 4
f
H
o n
C P U r u n
f
S Y S
o n
f
L I R C
o n
W D T o n
I D L E 1
H A L T i n s t r u c t i o n i s e x e c u t e d
C P U s t o p
I D L E N = 1
F S Y S O N = 1
f
S Y S
o n
f
L I R C
o n
W D T o n
I D L E 0
H A L T i n s t r u c t i o n i s e x e c u t e d
C P U s t o p
I D L E N = 1
F S Y S O N = 0
f
S Y S
o f f
f
L I R C
o n
W D T o n
S L O W
f
S Y S
= f
L
f
L
o n
C P U r u n
f
S Y S
o n
f
L I R C
o n
f
H
o f f
W D T o n
S L E E P
H A L T i n s t r u c t i o n i s e x e c u t e d
f
S Y S
o f f
C P U s t o p
I D L E N = 0
f
L I R C
o n
W D T o n
