3 i2c write cycle description, 4 i2c read cycle description, Tfa9812 – NXP Semiconductors TFA9812 User Manual

Page 28: Nxp semiconductors, C write cycle description, C read cycle description

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TFA9812_2

© NXP B.V. 2009. All rights reserved.

Preliminary data sheet

Rev. 02 — 22 January 2009

28 of 66

NXP Semiconductors

TFA9812

BTL stereo Class-D audio amplifier with I

2

S input

9.3 I

2

C write cycle description

Table 25

shows the cycle required for writing data to the I

2

C registers of the TFA9812. The

byte size is 8 bits. The I

2

C registers of the TFA9812 store two data bytes. Data is always

written in pairs of two bytes. Data transfer is always MSB first.

The cycle format for writing to the TFA9812 using SDA is as follows:

1. The microcontroller asserts a start condition (S).

2. The microcontroller sends the device address (7 bits) of the TFA9812 followed by the

R/!W bit set to 0.

3. The TFA9812 asserts an acknowledge (A).

4. The microcontroller writes the 8-bit TFA9812 register address to which the first data

byte will be written.

5. The TFA9812 asserts an acknowledge.

6. The microcontroller sends the first byte. This is the most significant byte of the

register.

7. The TFA9812 asserts an acknowledge.

8. The microcontroller sends the second byte.

9. The TFA9812 asserts an acknowledgement.

10. The microcontroller can either assert the stop condition (P) or continue with a further

pair of data bytes, repeating step 6. In the latter case the targeted register address will
have been auto-increased by the TFA9812.

9.4 I

2

C read cycle description

Table 26

shows the cycle required for reading data from the I

2

C registers of the TFA9812.

The byte size is 8 bits. The I

2

C registers of the TFA9812 store two data bytes. Data is

always read in pairs of two bytes. Data transfer is always MSB-first.

The read cycle format for writing to the TFA9812 using SDA is as follows:

1. The microcontroller asserts a start condition (S).

2. The microcontroller sends the device address (7 bits) of the TFA9812 followed by the

R/!W bit set to 0.

3. The TFA9812 asserts an acknowledge (A).

4. The microcontroller writes the 8-bit TFA9812 register address from which the first data

byte will be read.

5. The TFA9812 asserts an acknowledge.

6. The microcontroller asserts a repeated start (Sr).

7. The microcontroller resends the device address (7 bits) of the TFA9812 followed by

the R/!W bit set to 1.

8. The TFA9812 asserts an acknowledge.

Table 25.

I

2

C write cycle

Start

TFA9812
Address

R/!W

TFA9812 first
register address

MS
databyte

LS
databyte

More
data...

Stop

S

11010A

2

A

1

0

A

ADDR

A

MS1

A

LS1

<....>

P

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