ISL12023IVZ【PDF 15/29 页】IC RTC/CLDR TEMP SNSR 14-TSSOP

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Sheet目录2001

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ISL12023

FN6682.3

December 6, 2011

ALPHA Hot Register (ALPHAH)

The ALPHA Hot variable is 7 bits and is defined as the temperature

coefficient of Crystal from the XT0 value to +85°C (both Alpha Hot

and Alpha Cold must be programmed to provide full temperature

compensation). It is normally given in units of ppm/°C2, with a

typical value of -0.034. Like the ALPHA Cold version, a scaled

version of the absolute value of this coefficient is used in order to

get an integer value. Therefore, ALP_H<7:0> is defined as the

(|Actual Alpha Hot Value| x 2048) and converted to binary. For

example, a crystal with Alpha Hot of -0.034ppm/°C2 is first scaled

(|2048*(-0.034)| = 70d) and then converted to a binary number

of 01000110b.

The practical range of Actual ALPHAH values is from -0.020 to -

0.060.

The ISL12023 has a preset ALPHAH value corresponding to the

crystal in the module. This value is recalled on initial power-up

and should never be changed for best temperature

compensation performance, although the user may override this

preset value if so desired.

The ALPHAH register should only be changed while the TSE

(Temp Sense Enable) bit is “0”.

User Registers (Accessed by

Using Slave Address 1010111x)

Addresses [00h to 7Fh]

These registers are 128 bytes of battery-backed user SRAM. The

separate I2C slave address must be used to read and write to

these registers.

I2C Serial Interface

The ISL12023 supports a bi-directional bus oriented protocol.

The protocol defines any device that sends data onto the bus as a

transmitter and the receiving device as the receiver. The device

controlling the transfer is the master and the device being

controlled is the slave. The master always initiates data transfers

and provides the clock for both transmit and receive operations.

Therefore, the ISL12023 operates as a slave device in all

applications.

All communication over the I2C interface is conducted by sending

the MSB of each byte of data first.

Protocol Conventions

Data states on the SDA line can change only during SCL LOW

periods. SDA state changes during SCL HIGH are reserved for

indicating START and STOP conditions (see Figure 14). On power-up

of the ISL12023, the SDA pin is in the input mode.

All I2C interface operations must begin with a START condition,

which is a HIGH to LOW transition of SDA while SCL is HIGH. The

ISL12023 continuously monitors the SDA and SCL lines for the

START condition and does not respond to any command until this

condition is met (see Figure 14). A START condition is ignored

during the power-up sequence.

All I2C interface operations must be terminated by a STOP

condition, which is a LOW to HIGH transition of SDA while SCL is

HIGH (see Figure 14). A STOP condition at the end of a read

operation or at the end of a write operation to memory only

places the device in its standby mode.

An acknowledge (ACK) is a software convention used to indicate

a successful data transfer. The transmitting device, either master

or slave, releases the SDA bus after transmitting 8 bits. During

the ninth clock cycle, the receiver pulls the SDA line LOW to

acknowledge the reception of the 8 bits of data (see Figure 15).

The ISL12023 responds with an ACK after recognition of a START

condition followed by a valid Identification Byte, and once again

after successful receipt of an Address Byte. The ISL12023 also

responds with an ACK after receiving a Data Byte of a write

01000

29.0

00111

28.5

00110

28.0

00101

27.5

00100

27.0

00011

26.5

00010

26.0

00001

25.5

00000

25.0

10000

25.0

10001

24.5

10010

24.0

10011

23.5

10100

23.0

10101

22.5

10110

22.0

10111

21.5

11000

21.0

11001

20.5

11010

20.0

11011

19.5

11100

19.0

11101

18.5

11110

18.0

11111

17.5

TABLE 27. ALPHAH REGISTER

ADD

4321

2Dh

ALP_H

TABLE 26. XT0 VALUES (Continued)

XT<4:0>

TURNOVER TEMPERATURE

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