CS44800 datasheet(37/80 Pages) CIRRUS

37 / 80 page

DS632F1

CS44800

4.6.2

I²C Mode

In I²C mode, SDA is a bidirectional data line. Data is clocked into and out of the part by the clock, SCL.

There is no CS pin. Pins AD0 and AD1 form the two least significant bits of the chip address and should

be connected through a resistor to VLC or GND as desired. The state of the pins is sensed while the

CS44800 is being reset.

The signal timings for a read and write cycle are shown in Figure 25 and Figure 26. A Start condition is

defined as a falling transition of SDA while the clock is high. A Stop condition is a rising transition while

the clock is high. All other transitions of SDA occur while the clock is low. The first byte sent to the

CS44800 after a Start condition consists of a 7 bit chip address field and a R/W bit (high for a read, low

for a write). The upper 5 bits of the 7-bit address field are fixed at 10011. To communicate with a CS44800,

the chip address field, which is the first byte sent to the CS44800, should match 10011 followed by the

settings of the AD1 and AD0. The eighth bit of the address is the R/W bit. If the operation is a write, the

next byte is the Memory Address Pointer (MAP) which selects the register to be read or written. If the op-

eration is a read, the contents of the register pointed to by the MAP will be output. Setting the auto incre-

ment bit in MAP allows successive writes of consecutive registers. Each byte is separated by an

acknowledge bit. The ACK bit is output from the CS44800 after each input byte is read, and is input to the

CS44800 from the microcontroller after each transmitted byte. Autoincrement reads are not supported.

Since the read operation can not set the MAP, an aborted write operation is used as a preamble. As

shown in Figure 26, the write operation is aborted after the acknowledge for the MAP byte by sending a

stop condition. The following pseudocode illustrates an aborted write operation followed by a read oper-

ation.

Send start condition.

Send 10011xx0 (chip address & write operation).

Receive acknowledge bit.

Send MAP byte, auto increment off.

Receive acknowledge bit.

Send stop condition, aborting write.

Send start condition.

Send 10011xx1(chip address & read operation).

24 25

SCL

CHIP ADDRESS (WRITE)

MAP BYTE

DATA

DATA +1

START

ACK

STOP

ACK

1 AD1 AD0 0

SDA

INCR

16 17 18

10 11

13 14 15

27 28

DATA +n

Figure 25. Control Port Timing, I²C Slave Mode Write

SCL

CHIP ADDRESS (WRITE)

MAP BYTE

DATA

DATA +1

START

ACK

STOP

ACK

1 AD1 AD0 0

SDA

1 AD1 AD0 1

CHIP ADDRESS (READ)

START

INCR

12 13 14 15

20 21 22 23 24

26 27 28

10 11

17 18

ACK

DATA + n

STOP

Figure 26. Control Port Timing, I²C Slave Mode Read

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