BS85B12-3/BS85C20-3/BS85C20-5
Touch Key Flash MCU with LCD/LED Driver
CTRL Register
Bit
Name
R/W
7
6
5
4
3
2
1
D1
R/W
0
0
—
—
—
—
—
—
HIRCS1 HIRCS0
—
—
—
—
—
—
D0
R/W
R/W
0
R/W
0
POR
0
"x" ꢀnknown
Bitꢀ7~6ꢀ
Bitꢀ5~4ꢀ
unimplemented,ꢀreadꢀasꢀ"0"
HIRCS1, HIRCS0:ꢀHighꢀfrequencyꢀclockꢀselectꢀ
ꢀ 00:ꢀ8MHzꢀ
ꢀ 01:ꢀ16MHzꢀ
ꢀ 10:ꢀ12MHzꢀ
ꢀ 11:ꢀ8MHz
Bitꢀ3~2ꢀꢀ
Bitꢀ1~0ꢀ
unimplemented,ꢀreadꢀasꢀ"0"
D1, D0:ꢀTheseꢀbitsꢀmustꢀbeꢀsetꢀtoꢀtheꢀbinaryꢀvalueꢀ"00"
External 32.768kHz Crystal Oscillator – LXT (BS85C20-5 only)
ForꢀtheꢀBS85C20-5,ꢀthereꢀisꢀanꢀadditionalꢀexternalꢀ32.768kHzꢀcrystalꢀoscillatorꢀthatꢀisꢀusedꢀasꢀaꢀ
clockꢀsourceꢀforꢀTimeꢀBase.ꢀThisꢀclockꢀsourceꢀhasꢀaꢀfixedꢀfrequencyꢀofꢀ32.768kHzꢀandꢀrequiresꢀ
aꢀ32.768kHzꢀcrystalꢀtoꢀbeꢀconnectedꢀbetweenꢀpinsꢀOSC1ꢀandꢀOSC2.ꢀTheꢀexternalꢀresistorꢀandꢀ
capacitorꢀcomponentsꢀconnectedꢀtoꢀtheꢀ32.768kHzꢀcrystalꢀareꢀnecessaryꢀtoꢀprovideꢀoscillation.ꢀForꢀ
applicationsꢀwhereꢀpreciseꢀfrequenciesꢀareꢀessential,ꢀtheseꢀcomponentsꢀmayꢀbeꢀrequiredꢀtoꢀprovideꢀ
frequencyꢀcompensationꢀdueꢀtoꢀdifferentꢀcrystalꢀmanufacturingꢀtolerances.ꢀDuringꢀpower-upꢀthereꢀisꢀ
aꢀtimeꢀdelayꢀassociatedꢀwithꢀtheꢀLXTꢀoscillatorꢀwaitingꢀforꢀitꢀtoꢀstart-upꢀandꢀstabilise.ꢀ
TheꢀexactꢀvaluesꢀofꢀC1ꢀandꢀC2ꢀshouldꢀbeꢀselectedꢀinꢀconsultationꢀwithꢀtheꢀcrystalꢀorꢀresonatorꢀ
manufacturer’sꢀspecification.ꢀTheꢀexternalꢀparallelꢀfeedbackꢀresistor,ꢀRp,ꢀisꢀnormallyꢀrequired.
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7
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F
External LXT Oscillator
LXT Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
10pF
32.768kHz
10pF
Note:1. C1 and C2 valꢀes are for ꢁꢀidance only.
2. RP= 5M~10MΩ is recommended.
32.768kHz Crystal Recommended Capacitor Values
Rev. 1.20
43
�ꢀꢁꢀst 10ꢂ 2012
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
