NCP81233MNTXG Datasheet NCP81233MNTXG | P40-P42

NCP81233

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second data byte that is written to the register selected by the

address pointer register.

This write byte operation is shown in Figure 20. The

device address is sent over the bus, and then R/

W is set to

0. This is followed by two data bytes. The first data byte is

the address of the internal data register to be written to,

which is stored in the address pointer register. The second

data byte is the data to be written to the internal data register.

• The read byte operation is shown in Figure 21. First the

command code needs to be written to the NCP81233 so

that the required data is sent back. This is done by

performing a write to the NCP81233 as before, but only

the data byte containing the register address is sent,

because no data is written to the register. A repeated

start is then issued and a read operation is then

performed consisting of the serial bus address; R/

W bit

set to 1, followed by the data byte read from the data

• It is not possible to read or write a data byte from a data

the correct value.

• In addition to supporting the send byte, the NCP81233

also supports the read byte, write byte, read word and

write word protocols.

Figure 19. Send Byte

D6 D5 D4 D3 D2 D1 D0

SCL

SDA

START BY

MASTER

ACK. BY

NCP81233

ACK. BY STOP BY

NCP81233 MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

000

A1 A0

R/W

1919

FRAME 2

COMMAND CODE

Figure 20. Write Byte

SCL

SDA

START BY

MASTER

ACK. BY

NCP81233

FRAME 1

SERIAL BUS ADDRESS BYTE

000

A1 A0

R/W

1919

ACK. BY

NCP81233

…

FRAME 2

COMMAND CODE

ACK. BY

NCP81233

FRAME 3

DATA BYTE

STOP BY

MASTER

…

SCL (CONTINUED)

SDA (CONTINUED)

D6 D5 D4 D3 D2 D1 D0

…

NCP81233

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Figure 21. Read Byte

D6 D5 D4 D3 D2 D1 D0

SCL

SDA

START BY

MASTER

ACK. BY

NCP81233

ACK. BY

NCP81233

FRAME 1

SERIAL BUS ADDRESS BYTE

000

A1 A0

R/W

1919

FRAME 2

COMMAND CODE

D6 D5 D4 D3 D2 D1 D0

SCL

SDA

REPEATED START

BY MASTER

ACK. BY

NCP81233

NO ACK. BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

000

A1 A0

R/W

1919

FRAME 2

COMMAND CODE

STOP BY

MASTER

Write Operations

The I

C specification defines several protocols for

different types of read and writes operations. The ones used

in the NCP81233 are discussed in this section. The

following abbreviations are used in the diagrams:

S—START

P—STOP

R—READ

W—WRITE

A—ACKNOWLEDGE

—NO ACKNOWLEDGE

The NCP81233 uses the following I

C write protocols.

Send Byte

In this operation, the master device sends a single

command byte to a slave device as follows:

1. The master device asserts a start condition on

SDA.

2. The master sends the 7-bit slave address followed

by the write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. The master sends a command code.

5. The slave asserts ACK on SDA.

6. The master asserts a stop condition on SDA and

the transaction ends.

For the NCP81233, the send byte protocol is used to clear

faults. This operation is shown in Figure 22.

Figure 22. Send Byte Command

SLAVE

ADDR ESS

COMMAND

CODE

AWSA P

5 6

If the master is required to read data from the register

immediately after setting up the address, it can assert a repeat

start condition immediately after the final ACK and carry

out a single byte read without asserting an intermediate stop

condition.

Write Byte

In this operation, the master device sends a command byte

and one data byte to the slave device as follows:

1. The master device asserts a start condition on

SDA.

2. The master sends the 7-bit slave address followed

by the write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. The master sends a command code.

5. The slave asserts ACK on SDA.

6. The master sends a data byte.

7. The slave asserts ACK on SDA.

8. The master asserts a stop condition on SDA and

the transaction ends.

The byte write operation is shown in Figure 23.

NCP81233

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Figure 23. Single Byte Write to a Register

SLAVE

ADDRESS

W A

DATA

SAA P

COMMAND

CODE

231567 84

Write Word

In this operation, the master device sends a command byte

and two data bytes to the slave device as follows:

1. The master device asserts a start condition on

SDA.

2. The master sends the 7-bit slave address followed

by the write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. The master sends a command code.

5. The slave asserts ACK on SDA.

6. The master sends the first data byte.

7. The slave asserts ACK on SDA.

8. The master sends the second data byte.

9. The slave asserts ACK on SDA.

10. The master asserts a stop condition on SDA and

the transaction ends.

The word write operation is shown in Figure 24.

Figure 24. Single Word Write to a Register

SLAVE

ADDRESS

DATA

(LSB)

SAA

COMMAND

CODE

23156784

DATA

(MSB)

910

Block Write

In this operation, the master device sends a command byte

and a byte count followed by the stated number of data bytes

to the slave device as follows:

1. The master device asserts a START condition on

SDA.

2. The master sends the 7-bit slave address followed

by the write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. The master sends a command code.

5. The slave asserts ACK on SDA.

6. The master sends the byte count N.

7. The slave asserts ACK on SDA.

8. The master sends the first data byte.

9. The slave asserts ACK on SDA.

10. The master sends the second data byte.

11. The slave asserts ACK on SDA.

12. The master sends the remainder of the data byes.

13. The slave asserts an ACK on SDA after each data

byte.

14. After the last data byte the master asserts a STOP

condition on SDA.

Figure 25. Block Write to a Register

SLAVE

ADDRESS

W A

BYTE COUNT

SAA

COMMAND

CODE

23156784

DATA

BYTE 1

DATA

BYTE N

DATA

BYTE 2

13 14

Read Operations

The NCP81233 uses the following I

C read protocols.

Read Byte

In this operation, the master device receives a single byte

from a slave device as follows:

1. The master device asserts a start condition on

SDA.

2. The master sends the 7-bit slave address followed

by the write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. The master sends a command code.

5. The slave asserted ACK on SDA.

6. The master sends a repeated start condition on

SDA.

7. The master sends the 7 bit slave address followed

by the read bit (high).

8. The slave asserts ACK on SDA.

9. The slave sends the Data Byte.

10. The master asserts NO ACK on SDA.

11. The master asserts a stop condition on SDA and

the transaction ends.

Figure 26. Single Byte Read to a Register

SLAVE

ADDRESS

W A

SLAVE

ADDRESS

SAA

COMMAND

CODE

23156784

DATA

A P

910

Read Word

In this operation, the master device receives two data

bytes from a slave device as follows:

1. The master device asserts a start condition on

SDA.

2. The master sends the 7-bit slave address followed

by the write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. he master sends a command code.

5. The slave asserted ACK on SDA.

6. The master sends a repeated start condition on

SDA.

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NCP81233MNTXG

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