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2015-06-0002

PT0322-8

06/16/15

8

PT7C4311

Real-time Clock Module (I

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.

(hex)

Description

D7

D6

D5

D4

D3

D2

D1

D0

07

Control

OUT

FT

S

Calibration

(default)

1

0

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.

Default

0

Set low level at pin 7.

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.

Default

1

Enable 512Hz output at pin 7.

c)

Calibration bits



S: Sign bit.

S

Data

Description

Read / Write

1

Indicate positive calibration.

Default

0

Indicate negative calibration.

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.