Maxim manual MAX9777 I2C Slave Addresses, MAX9777/MAX9778

Stereo 3W Audio Power Amplifiers with Headphone Drive and Input Mux

Early STOP Conditions The MAX9777 recognizes a STOP condition at any point during the transmission except if a STOP condi- tion occurs in the same high pulse as a START condi- tion (Figure 5). This condition is not a legal I2C format; at least one clock pulse must separate any START and STOP condition.

REPEATED START Conditions

AREPEATED START (Sr) condition may indicate a change of data direction on the bus. Such a change occurs when a command word is required to initiate a

read operation. Sr may also be used when the bus master is writing to several I2C devices and does not want to relinquish control of the bus. The MAX9777 ser- ial interface supports continuous write operations with or without an Sr condition separating them. Continuous read operations require Sr conditions because of the change in direction of data flow.

SCL

SDA

STOPSTART

LEGAL STOP CONDITION

SCL

SDA

STARTILLEGAL

STOP

ILLEGAL EARLY STOP CONDITION

Figure 5. Early STOP Condition

Acknowledge Bit (ACK) The acknowledge bit (ACK) is the ninth bit attached to any 8-bit data word. The receiving device always gen- erates ACK. The MAX9777 generates an ACK when receiving an address or data by pulling SDA low during the night clock period. When transmitting data, the MAX9777 waits for the receiving device to generate an ACK. Monitoring ACK allows for detection of unsuc- cessful 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 should reattempt communica- tion at a later time.

Slave Address The bus master initiates communication with a slave device by issuing a START condition followed by a 7-bit slave address (Figure 6). When idle, the MAX9777 waits for a START condition followed by its slave

address. The LSB of the address word is the Read/Write (R/W) bit. R/W indicates whether the master

is writing to or reading from the MAX9777 (R/W = 0 selects the write condition, R/W = 1 selects the read condition). After receiving the proper address, the MAX9777 issues an ACK by pulling SDA low for one clock cycle.

The MAX9777 has a factory-/user-programmed address. Address bits A6–A2 are preset, while A0 and A1 is set by ADD. Connect ADD to either VDD, GND, SCL, or SDA to change the last 2 bits of the slave address (Table 2).

S A6 A5 A4 A3 A2 A1 A0 R/W

Figure 6. Slave Address Byte Definition

Table 2. MAX9777 I2C Slave Addresses

ADD CONNECTION	I2C ADDRESS
GND	100 1000
VDD	100 1001
SDA	100 1010
SCL	100 1011

MAX9777/MAX9778

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