BS83B08-3 Datasheet, PDF (38/141 Pages) Holtek Semiconductor Inc – 8-Bit Touch Key Flash MCU

BS83B08-3/B12-3/B16-3/B16G-3/C24-3
8-Bit Touch Key Flash MCU
Operating Modes and System Clocks
Present day applications require that their microcontrollers have high performance but often still
demand that they consume as little power as possible, conflicting requirements that are especially true
in battery powered portable applications. The fast clocks required for high performance will by their
nature increase current consumption and of course vice-versa, lower speed clocks reduce current
consumption. As Holtek has provided these devices with both high and low speed clock sources and
the means to switch between them dynamically, the user can optimise the operation of their
microcontroller to achieve the best performance/power ratio.
System Clocks
The main system clock, can come from either a high frequency, f_H, or low frequency, f_L, source, and is
selected using the HLCLK bit and CKS2~CKS0 bits in the SMOD register. Both the high and low
speed system clocks are sourced from internal RC oscillators.
H ig h S p e e d O s c illa to r
H IR C
fH IR C
8 M H z /1 2 M H z /1 6 M H z
H ig h S p e e d C lo c k S e le c t
H IR C S 0 , H IR C S 1 b its
f L IR C
L IR C
32kH z
L o w S p e e d O s c illa to r
P e r m a n e n tly E n a b le d
6 - s ta g e P r e s c a le r
fH IR C /n
n = (2 , 4 , 8 , 1 6 , 3 2 o r 6 4 )
M
U
X
32kH z
C lo c k S e le c t
C K S 0 ~ C K S 2 b its
f L IR C
f H IR C
f L IR C
W a tc h d o g T im e r
T im e r /E v e n t C o u n te r
fH IR C /n o r fL IR C
M
U
fS Y S
X
F a s t/S lo w
C lo c k S e le c t
H C L K b it
f L IR C
T im e B a s e
S LE E P
T im e B a s e c lo c k s o u r c e
d is a b le d in S lE E P M o d e
System Clock Configurations
Rev. 1.30
38
September 22, 2011