MAX32660 User Guide
Maxim Integrated
Page 134 of 195
•
Address 0b0000 x
4
x
3
x
2
x
1
is reserved by the I
2
C specification for special purposes and should not be used for a slave
address.
•
Address 0b1111 1 x
3
x
2
x
1
is reserved by the I
2
C specification for special purposes and should not be used for a slave
address.
12.3.6
Acknowledge and Not Acknowledge
An acknowledge bit (ACK) is generated by the receiver, whether I
2
C master or slave, after every byte received. The ACK bit is
how the receiver tells the transmitter that the byte was successfully received, and another byte might be sent.
A Not Acknowledge (NACK) occurs if the receiver does not generate an ACK when the transmitter releases SDA. A NACK
allows SDA to float high during the acknowledge time slot. The I
2
C master can then either generate a STOP condition to
abort the transfer, or it can generate a repeated START condition (that is, send a START condition without an intervening
STOP condition) to start a new transfer.
A receiver can generate a NACK after a byte transfer if any of the following conditions occur:
•
No receiver is present on the bus with the transmitted address. In that case, no device will respond with an
acknowledge signal.
•
The receiver is unable to receive or transmit because it is busy and is not ready to start communication with the
master.
•
During the transfer, the receiver receives data or commands it does not understand.
•
During the transfer, the receiver is unable to receive any more data.
•
If an I
2
C master has requested data from a slave, it signals the slave to stop transmitting by sending a NACK
following the last byte it requires.
12.3.7
Bit Transfer Process
Both SDA and SCL circuits are open-drain, bidirectional circuits. Each has an external pullup resistor that ensures each
circuit is high when idle. The I
2
C specification states that during data transfer, the SDA line can change state only when SCL
is low, and that SDA is stable and able to be read when SCL is high as shown in
Figure 12-2: I
2
C Write Data Transfer
