PT7C4311 Datasheet, PDF (8/16 Pages) Pericom Semiconductor Corporation – Real-time Clock Module

PT7C4311
Real-time Clock Module (I²C Bus)
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08~3F RAM
Caution points:
*1. PT7C4311 uses 6 bits for address. That is if write data to 41H, the data will be written to 01H address register.
*2. Stop bit. When this bit is set to 1, oscillator and time count chain are both stopped.
*3. CEB: Century Enable Bit. CB: Century Bit.
*4. Control FT/OUT pin output DC level when 512Hz square wave is disabled.
*5. Frequency Test. 512Hz square wave output is enabled at FT/OUT pin, which is using for frequency test.
*6. Sign Bit. “1” indicates positive calibration; “0”indicates negative calibration.
*7. Using for modifying count frequency. If 20ppm is wanted to slow down the count frequency, 10 (01010) should be loaded.
*8. Initialize the control and status register to 10000000 if calibration function is not required.
2. Control and status register
Addr.
Description
D7
D6
D5
D4
D3
D2
D1
D0
(hex)
07
Control
(default)
OUT
FT
1
0
S
Calibration
1
Undefined Undefined Undefined Undefined Undefined
a) OUT
 OUT: Set pin 7 output DC level..
OUT
Data
Description
Read / Write
1 _{Set high level at pin 7.}
0 _{Set low level at pin 7.}
Default
b) 512Hz output
 FT: 512Hz square wave output Enable bit, using for Frequency Test.
FT
Data
Description
Read / Write
0 _{Disable 512Hz output at pin 7.}
1 _{Enable 512Hz output at pin 7.}
Default
c) Calibration bits
 S: Sign bit.
S
Data
Description
Read / Write
1 _{Indicate positive calibration.}
0 _{Indicate negative calibration.}
Default
Calibration:
Calibration occurs within a 64minute cycle. The first 62 minutes in the cycle may, once per minute, have one second either
shortened by 128 or lengthened by 256 oscillator cycles. If a binary '1' is loaded into the register, only the first 2
minutes in the 64 minute cycle will be modified; if a binary 6 is loaded, the first 12 will be affected, and so on. Therefore, each
calibration step has the effect of adding 512 or subtracting 256 oscillator cycles for every 125,829,120 actual oscillator cycles, that
is +4.068 or –2.034 ppm of adjustment per calibration step in the calibration register. Assuming that the oscillator is in fact
running at exactly 32,768Hz, each of the 31 increments in the Calibration byte would represent +10.7 or –5.35 seconds per month
which corresponds to a total range of +5.5 or –2.75 minutes per month.
For example, a reading of 512.01024Hz would indicate a +20 ppm oscillator frequency error, requiring a –10 (XX001010) to be
loaded into the Calibration Byte for correction.
2015-06-0002
PT0322-8
06/16/15
8