PT7C4300 PERICOM [Pericom Semiconductor Corporation], PT7C4300 Datasheet - Page 6

• Manufacturer Part Number: PT7C4300
• Manufacturer: PERICOM [Pericom Semiconductor Corporation]

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2.
a)
•
b)
•
c)
•
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. Note that setting or changing the Calibration Byte does not affect the Frequency
test output frequency.
PT0222(02/06)
Addr.
(hex)
07
OUT: Set pin 7 output DC level..
FT: 512Hz square wave output Enable bit, using for Frequency Test.
S: Sign bit.
Read / Write
Read / Write
Read / Write
Control and status register
OUT
512Hz output
Calibration bits
OUT
FT
S
Description
(default)
Control
Data
Data
Data
Clock calibration
1
0
0
1
1
0
OUT
Set high level at pin 7.
Set low level at pin 7.
Disable 512Hz output at pin 7.
Enable 512Hz output at pin 7.
Indicate positive calibration.
Indicate negative calibration.
D7
0
D6
FT
0
D5
S
1
6
D4
1
Description
Description
Description
Real-time Clock Module (I
D3
1
Calibration
D2
1
D1
1
Data Sheet
PT7C4300
2
C Bus)
Default
Default
Default
D0
Ver: 0
1