ALS-PDIC17-79NB-TR8 Datasheet, PDF (9/21 Pages) Everlight Electronics Co., Ltd – I2 Digital Ambient Light Sensor

Surface - Mount
I²C Digital Ambient Light Sensor
ALS-PDIC17-79NB/TR8
Communication Format
ALS-PDIC17-79NB is capable of working as an I²C slave. Address of this device on I²C bus is always
0x39 (hexadecimal number 39). Registers of the slave device can be programmed by sending commands
over I²C bus.
Figure 12 shows an I²C write operation. To write to an internal register of the slave device a command
must be sent by an I²C master. As illustrated in Figure 12, the I²C write command begins with a start condition.
After the start condition, seven bits of address are sent with MSB going first. RD / WRn (=Low) command bit
follows the address bits. Upon receiving a valid address the slave device responds by driving SDA low for an
ACK. After receiving an ACK, I²C master sends eight bits of data with MSB first. Upon receiving eight bits of
data the slave device generates an ACK. I²C master terminates this write command with a stop condition.
START
Device Address 0x39 (Hex) ^{R/W A}
Command to Device
A
STOP
SDA
(Master OUT)
A6 A5 A4 A3 A2 A1 A0 _W A R7 R6 R5 R4 R3 R2 R1 R0 A
SDA
(Slave OUT)
SCL
(Master OUT)
SDAdriven byMaster
A
SDAdriven byMaster
A
123456789123456789
Figure 12. I²C Timing Diagram for Send Byte Format
Figure 13 shows an I²C read command sent by the master to the slave device. I²C read command
begins with a start condition. After the start condition seven bits of address are sent by the master with MSB
going first. After the address bits, RD / WRn command bit is sent. For a read command the RD / WRn bits is
high. Upon receiving the address bits and RD / WRn command bits the slave device responds with an ACK.
After sending an ACK, the slave device sends eight bits of data with MSB going first. After receiving the one
byte data, the I²C master terminates this transaction by issuing a NACK command to indicate that the master
only wanted to read one byte from the device. The master generates a stop condition to end this transaction.
Everlight Electronics Co., Ltd.
Document No: DLS-xxxxxxx Rev1
9
http://www.everlight.com
Oct. 12, 2010