MAX44004 Datasheet, PDF (14/17 Pages) Maxim Integrated Products – Digital Ambient Light Sensor

MAX44004
Digital Ambient Light Sensor
START and STOP Conditions
SDA and SCL idle high when the bus is not in use. A mas-
ter initiates communication by issuing a START condition.
A START condition is a high-to-low transition on SDA with
SCL high. A STOP condition is a low-to-high transition on
SDA while SCL is high (Figure 5). A START condition from
the master signals the beginning of a transmission to the
device. The master terminates transmission, and frees
the bus by issuing a STOP condition. The bus remains
active if a Repeated START condition is generated
instead of a STOP condition.
Early STOP Conditions
The device recognizes a STOP condition at any point
during data transmission, except if the STOP condition
occurs in the same high pulse as a START condition. For
proper operation, do not send a STOP condition during
the same SCL high pulse as the START condition.
Acknowledge
The acknowledge bit (ACK) is a clocked 9th bit that the
device uses to handshake receipt of each byte of data
when in write mode (Figure 6). The device pulls down
SDA during the entire master-generated 9th clock pulse
if the previous byte is successfully received. Monitoring
ACK allows for detection of unsuccessful data transfers.
An unsuccessful data transfer occurs if a receiving
device is busy or if a system fault has occurred. In the
event of an unsuccessful data transfer, the bus master
may retry communication. The master pulls down SDA
during the 9th clock cycle to acknowledge receipt of data
when the device is in read mode. An acknowledge is sent
by the master after each read byte to allow data transfer
to continue. A not acknowledge is sent when the master
reads the final byte of data from the device, followed by
a STOP condition.
Write Data Format
A write to the device includes transmission of a START
condition, the slave address with the R/W bit set to 0, 1
byte of data to configure the internal register address
pointer, 1 or more bytes of data, and a STOP condition.
Figure 7 illustrates the proper frame format for writing 1
byte of data to the device. Figure 8 illustrates the frame
format for writing n bytes of data to the device.
The slave address with the R/W bit set to 0 indicates that
the master intends to write data to the device. The device
acknowledges receipt of the address byte during the
master-generated 9th SCL pulse.
S
SCL
SDA
Sr
P
Figure 5. START, STOP, and Repeated START Conditions
START
CONDITION
SCL
1
2
SDA
Figure 6. Acknowledge
CLOCK PULSE FOR
ACKNOWLEDGMENT
8
9
NOT ACKNOWLEDGE
ACKNOWLEDGE
ACKNOWLEDGE FROM MAX44004
ACKNOWLEDGE FROM MAX44004
ACKNOWLEDGE FROM MAX44004
B7 B6 B5 B4 B3 B2 B1 B0
S
SLAVE ADDRESS
0A
REGISTER ADDRESS
A
DATA BYTE
AP
R/W
1 BYTE
Figure 7. Writing 1 Byte of Data to the MAX44004
14