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BQ32000 Datasheet, PDF (15/20 Pages) Texas Instruments – REAL-TIME CLOCK (RTC)
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bq32000
www.ti.com................................................................................................................................................... SLUS900B – DECEMBER 2008 – REVISED JUNE 2009
Special Function Registers
Address
Name
Initial Value
Description
D7
0
0
SF KEY B1
0x20
SF KEY 1
00000000b
Special function key 1
SF KEY 1 Register
D6
D5
D4
D3
D2
D1
D0
BIT(S)
SF KEY B1
Name
r/w
Read/Write
0
0
0
0
0
0
0
Initial
0
0
0
0
0
0
0
Cycle
Special function access key byte 1. Reads as 0x00, and key is 0x5E.
The SF KEY 1 and SF KEY 2 registers are used to enable access to the main special function register (SFR). Access to
SFR is granted only after the special function keys are written sequentially to SF KEY 1 and SF KEY 2. Each write to the
SFR must be preceded by writing the SF keys to the SF key registers, in order, SF KEY 1 then SF KEY 2.
Address
Name
Initial Value
Description
D7
0
0
SF KEY 2
0x21
SF KEY 2
00000000b
Special function key 2
SF KEY 2 Register
D6
D5
D4
D3
D2
D1
D0
BIT(S)
SF KEY 2
Name
r/w
Read/Write
0
0
0
0
0
0
0
Initial
0
0
0
0
0
0
0
Cycle
Special function access key byte 2. Reads as 0x00, and key is 0xC7.
The SF KEY 1 and SF KEY 2 registers are used to enable access to the main special function register (SFR). Access to
SFR is granted only after the special function keys are written sequentially to SF KEY 1 and SF KEY 2. Each write to the
SFR must be preceded by writing the SF keys to the SF key registers, in order, SF KEY 1 then SF KEY 2.
Address
Name
Initial Value
Description
D7
0
0
RSVD
FTF
0x22
SFR
00000000b
Special function register 1
SFR Register
D6
D5
D4
D3
D2
D1
D0
BIT(S)
RSVD
FTF
Name
r/w
r/w
Read/Write
0
0
0
0
0
0
0
Initial
0
0
0
0
0
0
0
Cycle
Reserved. The RSVD bits should always be written as 0.
Force calibration to 1 Hz. FTF allows the frequency of the calibration output to be changed from 512 Hz to 1 Hz. By
default, FTF is cleared, and the RTC outputs a 512-Hz calibration signal. Setting FTF forces the calibration signal to 1
Hz, and the calibration tracks the internal ppm adjustment. Note: The default 512-Hz calibration signal does not include
the effect of the ppm adjustment.
0
Normal 512-Hz calibration
1
1-Hz calibration
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