Data Sheet

ID, the MAX30105 issues an ACK by pulling SDA low for
one clock cycle.
The MAX30105 slave ID consists of seven fixed bits,
B7–B1 (set to 0b1010111). The most significant slave ID
bit (B7) is transmitted first, followed by the remaining bits.
Table 17 shows the possible slave IDs of the device.
Acknowledge
The acknowledge bit (ACK) is a clocked 9th bit that the
MAX30105 uses to handshake receipt of each byte of
data when in write mode (Figure 8). The MAX30105
pulls down SDA during the entire master-generated 9
th
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 retries communication. The master pulls down SDA
during the 9th clock cycle to acknowledge receipt of data
when the MAX30105 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 MAX30105,
followed by a STOP condition.
Write Data Format
For the write operation, send the slave ID as the first byte
followed by the register address byte and then one or
more data bytes. Terminate the data transfer with a STOP
condition. The write operation is shown in Figure 9.
The internal register address pointer increments auto-
matically, so writing additional data bytes fill the data
registers in order.
Figure 7. START, STOP, and REPEATED START Conditions
Figure 9. Writing One Data Byte to the MAX30105
Figure 8. Acknowledge
Table 17. Slave ID Description
B7 B6 B5 B4 B3 B2 B1 B0
WRITE
ADDRESS
READ
ADDRESS
1 0 1 0 1 1 1 RW 0xAE 0xAF
S Sr P
SCL1
SDA1
SCL1
SDA1
START
CONDITION
1 2 8 9
CLOCK PULSE FOR
ACKNOWLEDGMENT
NOT ACKNOWLEDGE
ACKNOWLEDGE
S
1 0 1 0 1 1 1
R/W
= 0
ACK A7 A6 A5 A4 A3 A2
SLAVE ID
A1 A0
ACK P
S = START CONDITION
P = STOP CONDITION
ACK = ACKNOWLEDGE BY THE RECEIVER
REGISTER ADDRESS
D7 D6 D5 D4 D3 D2 D1 D0
ACK
DATA BYTE
INTERNAL ADDRESS POINTER AUTO-INCREMENT (FOR WRITING MULTIPLE BYTES
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Maxim Integrated │ 30
MAX30105 High-Sensitivity Optical Sensor
for Smoke Detection Applications