32

DS624A1

CS5368

There is a MAP auto-increment capability, which is enabled by the INCR bit in the MAP register. If INCR

is a zero, the MAP will stay constant for successive read or writes. If INCR is set to a 1, the MAP will auto

increment after each byte is read or written, allowing block reads or writes of successive registers.

To read a register, the MAP has to be set to the correct address by executing a partial write cycle that

finishes (CS high) immediately after the MAP byte. The MAP auto increment bit (INCR) may be set or not,

as desired. To begin a read, bring CS low, send out the chip address and set the read/write bit (R/W) high.

The next falling edge of CCLK will clock out the MSB of the addressed register (CDOUT will leave the high

impedance state). If the MAP auto increment bit is set to 1, the data for successive registers will appear

consecutively

.

Figure 15. SPI Format

4.9.2

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 DGND as desired. The state of the pins is latched when the

CS5368 is being released from RST.

A Start condition is defined as a falling transition of SDA while SCL is high. A Stop condition is a rising

transition of SDA while SCL is high. All other transitions of SDA occur while SCL is low. The first byte sent

to the CS5368 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 five bits of the 7-bit address field are fixed at 10011. To communicate with a

CS5368

, the chip address field, which is the first byte sent to the CS5368, should match 10011 and be

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 operation is a read, the contents of the register pointed to by the MAP will be output. Setting

the auto increment bit in MAP allows successive reads or writes of consecutive registers. Each byte is

separated by an acknowledge bit. The ACK bit is output from the CS5368 after each input byte is read

and is input to the CS5368 from the microcontroller after each transmitted byte.

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

Send start condition.

Send 10011xx0 (chip address & write operation).

Receive acknowledge bit.

Send MAP byte, auto increment off.

Receive acknowledge bit.

MA P

MSB

LSB

DATA

by te 1

by te n

R/W

R/W

AD D R ESS

CH IP

ADDRESS

CH I P

CD I N

CC L K

CS

CD O U T

MSB

LSB MSB

LSB

1001111

1001111

MAP = Memory Address Pointer, 8 bits, MSB first

High Impedance