Cirrus-logic CS8406 User Manual download pdf (Page 17)

DS580F6 17

CS8406

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, AD1, and AD2 form the three least significant bits of the chip address and should

be connected to VL or GND as desired.

The signal timing for both a read and write cycle are shown in Figure 11 and Figure 12. 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 CS8406 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 4 bits of the 7-bit address field are fixed at 0010. To communicate with a CS8406, the chip address

field, which is the first byte sent to the CS8406, should match 0010 followed by the settings of the AD2, AD1,

and AD0 pins. 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 operation is a read,

the contents of the register pointed to by the MAP will be output. Th e MAP automatically increments, so

consecutive registers can read from or written to e asily. Each byte is se parated by an acknowled ge bit

(ACK). The ACK bit is output from the CS8406 after each input byte is read, and is input to the CS8406 from

the microcontroller after each transmitted byte.

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

in Figure 12, the write operation is aborted after the acknowledge for the MAP by sending a stop condition.

4 5 6 7 24 25

SCL

0 0 1 0 AD2 AD1 AD0 0

CHIP ADDRESS (WRITE) MAP DATA

DATA +1

START

ACK

STOP

ACKACKACK

SDA

6 5 4 3 2 1

7 6 1 0 7 6 1 0 7 6 1 0

0 1 2 3 8 9 12 16 17 18 19 10 11 13 14 15 27 28

DATA +n

Figure 11. Control Port Timing, I²C Slave Mode Write

SCL

CHIP ADDRESS (WRITE)

MAP

DATA

DATA +1

START

ACK

STOP

ACK

SDA

6 5 4 3 2 1 0

CHIP ADDRESS (READ)

START

7 0 7 0 7 0

16 8 9 12 13 14 15 4 5 6 7 0 1 20 21 22 23 24

26 27 28

2 3 10 11 17 18 19 25

ACK

DATA + n

STOP

0 0 1 0 AD2 AD1 AD0 0 0 0 1 0 AD2 AD1 AD0 1

Figure 12. Control Port Timing, I²C Slave Mode Read

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 38 39

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Cirrus-logic CS8406 User Manual Page 17

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