16

DS580F6

CS8406

6. CONTROL PORT DESCRIPTION

The control port is used to access the registers, allowing the CS8406 to be configured for the desired operational

modes and formats. The operation of the control port may be completely asynchronous with respect to the audio

sample rates. However, to avoid potential interference problems, the control port pins should remain static if no op-

eration is required.

The control port has two modes: SPI and I²C, with the CS8406 acting as a slave device. SPI Mode is selected if

there is a high to low transition on the AD0/CS pin, after the RST pin has been brought high. I²C Mode is selected

by connecting the AD0/CS pin through a resistor to VL or GND, thereby permanently selecting the desired AD0 bit

address state.

6.1

SPI Mode

In SPI Mode, CS is the CS8406 chip select signal, CCLK is the control port bit clock (input into the CS8406

from the microcontroller), CDIN is the input data line from the microcontroller, and CDOUT is the output data

line to the microcontroller. Data is clocked in on the rising edge of CCLK and out on the falling edge.

Figure 10 shows the operation of the control port in SPI Mode. To write to a register, bring CS low. The first

seven bits on CDIN form the chip address and must be 0010000. The eighth bit is a read/write indicator

(R/W), which should be low to write. The next eight bits form the Memory Address Pointer (MAP), which is

set to the address of the register that is to be updated. The next eight bits are the data which will be placed

into the register designated by the MAP. During writes, the CDOUT output stays in the Hi-Z state. It may be

externally pulled high or low with a 47 k resistor, if desired.

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

finishes (CS high) immediately after the MAP byte. 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 willclock out the MSB of the addressed

register (CDOUT will leave the high impedance state). The MAP automatically increments so data for suc-

cessive registers will appear consecutively.

MA P

MSB

LSB

DATA

by te 1

by te n

R/W

R/W

AD D R ESS

CH IP

ADDRESS

CH IP

CD IN

CC L K

CS

CD OU T

MSB

LSB MSB

LSB

0010000

0010000

MAP = Memory Address Pointer, 7 bits, MSB first

High Impedance

Figure 10. Control Port Timing in SPI Mode