CS8415A-CS datasheet(17/42 Pages) CIRRUS

17 / 42 page

CS8415A

6. CONTROL PORT DESCRIPTION AND

TIMING

The control port is used to access the registers, al-

lowing the CS8415A to be configured for the de-

sired operational modes and formats. In addition,

Channel Status and User data may be read

through the control port. The operation of the con-

trol port may be completely asynchronous with re-

spect to the audio sample rates. However, to avoid

potential interference problems, the control port

pins should remain static if no operation is re-

quired.

The control port has 2 modes: SPI and I2C, with the

CS8415A 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 to VL+ or DGND, thereby permanently

selecting the desired AD0 bit address state.

6.1

SPI Mode

In SPI mode, CS is the CS8415A chip select sig-

nal, CCLK is the control port bit clock (input into the

CS8415A from the microcontroller), CDIN is the in-

put data line from the microcontroller, 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 8 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 in-

dicator (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 designat-

ed 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

Ω resistor, if desired.

There is a MAP auto increment capability, enabled

by the INCR bit in the MAP register. If INCR is a ze-

ro, the MAP will stay constant for successive read

or writes. If INCR is set to a 1, the MAP will autoin-

crement 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

which 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

state). If the MAP auto increment bit is set to 1, the

data for successive registers will appear consecu-

tively.

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,

MA P

MSB

LSB

DATA

byte 1

by te n

R/W

AD D R ES S

CH IP

ADDRESS

CH IP

CD IN

CC L K

CD O U T

MSB

LSB MSB

LSB

0010000

MAP = Memory Address Pointer, 8 bits, MSB first

High Impedance

Figure 8. Control Port Timing in SPI Mode

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