LX1977

Microsemi

Analog Mixed Signal Group

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 15

SMBus Ambient Light Sensor

TM

®

Copyright

© 2010

Rev. 1.0, 2010-03-25

Note:

(1) When INT_FLAG of register 00h is cleared via SMBus command after an interrupt

response, the internal counter for INT_PERSIST_CTRL will be reset to 0.

(2) For out-of-range conditions in the same direction, the persistence counter increments. If

result is no longer out-of-range, the count starts over. If the output result is between the

thresholds (in-range), then counter resets to ‘0’. If the value goes out of range in the other

direction, the counter starts over at ‘1’.

(3) Note that once the interrupt is triggered and the INT pin is asserted low, the INT pin will

stay low until INT_FLAG bit is set to zero or INT_ENA is set to 0.

conversion mode.

Register 01h and Write / Read Byte Protocols application:

For programming register 01h, a Write Byte protocol should be used.

When using Write Byte / Word protocol to send command / data to registers (including register 00h), bit 7 in

command code field should be set to 0 to indicate this byte is for the register address. Other bits (bit 6, 5 & 4) except for

the Register Address bits (bit 3, 2, 1 & 0) need to be set to zero also. The detailed Write Byte / Read Byte protocols are

shown below.

Note: Register 01h should be set prior to register 00h in order to get meaningful ALS read out.

Table 25: Write Byte Protocol:

1

7

1

1

Bit 7

Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

1

8

1

S

Slave Address

Wr

A

CMD_FLAG

0

0

0

0

0

0

1

A

Data Byte

A

P

0

0

01h

Register 01h could be read back by the host by using a Read Byte protocol. When LX1977 receives a Read Byte

protocol, it will put register 01h data into the Data Byte field and send the data back to the host. Please see Table 11 &

Table 19 for details.

Table 26: Read Byte Protocol:

1

7

1

1

Bit 7

Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

1

1

7

1

1

8

1

S

Slave Address Wr

A

CMD_FLAG

0

0

0

0

0

0

1

A

S

Slave Address

Rd

A

Data Byte

A

P

0

0

01h

1

1

Examples of setting register 01h by using Write Byte Protocol

Write Byte protocol is shown below (only the Data Byte is in detail, please refer to Table 26).

Table 27: Write Byte Protocol:

1

7

1

1

1

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

1

1

S

Slave Address

Wr

A

Command Code

A

A

P

0

0

0

0

1

0

1

0

1

The above example will write data byte 15h into register 01h to set the following configurations: