CS4812 datasheet(26/36 Pages) CIRRUS

26 / 36 page

CS4812

DS291PP3

abled, data bytes sent following the first data byte

will be written to successive registers following

that designated in the MAP.

During a read sequence, multiple bytes may be read

by continuing to clock in data bytes to the CS4812

after the first data byte and before initiating a stop

condition. If auto increment is disabled, the last

data byte read will be the register designated by the

MAP. If auto increment is enabled, data bytes read

following the first data byte will be read from suc-

cessive registers following that designated in the

MAP.

3.6

Boot Modes

There are two different techniques that allow the

system to load the application code into the

CS4812. The first technique is called, “AutoBoot”

and allows the application code to be loaded from

an external serial EEPROM with an I2C or SPI in-

terface. This technique is used in system applica-

tions that due not have a host. The second

technique is called, “Host Boot” and allows the ap-

plication code to be loaded directly from the host

microcontroller via I2C or SPI communication in-

terface. This method may eliminate the need for an

external EEPROM.

3.6.1

AutoBoot

The AutoBoot method simply requires an external

EEPROM with an I2C or SPI serial bus interface.

The DSP, automatically loads and runs the applica-

tion code resident in the EEPROM upon deasser-

tion of the RESET line. It should be noted that this

technique is used for systems that do not have a mi-

crocontroller and do not require real-time adjust-

ment of the application code parameters. Please

refer to Table 10 on page 6 for the timing require-

ments of the RESET line.

3.6.2

HostBoot

By using the HostBoot technique, an external mi-

crocontroller is required to download the applica-

Figure 25. I2C Slave Mode Read from DSP Core

Flow Diagram with DSP REQ

REQ LOW?

SEND I2C START

WRITE ADDRESS BYTE

WITH R/W BIT = 0

GET ACK

READ DATABYTE

REQ STILL LOW?

SEND ACK

SEND NACK

SEND I2C STOP

GET ACK

WRITE ADDRESS BYTE

WITH R/W BIT = 1

GET ACK

SEND I2C START

SEND MAP BYTE

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