MCP4017 datasheet(38/66 Pages) MICROCHIP

38 / 66 page

MCP4017/18/19

DS22147A-page 38

5.4.1

WRITE OPERATION

The write operation requires the START condition,

Control Byte, Acknowledge, Data Byte, Acknowledge

and STOP (or RESTART) condition. The Control (Slave

Address) Byte requires the R/W bit equal to a logic zero

(R/W = “0”) to generate a write sequence. The

MCP4017/18/19 is responsible for generating the

Acknowledge (A) bits.

Data is written to the MCP4017/18/19 after every byte

transfer (during the A bit). If a STOP or RESTART

condition is generated during a data transfer (before

the A bit), the data will not be written to MCP4017/18/

19.

Data bytes may be written after each Acknowledge.

The command is terminated once a Stop (P) condition

occurs. Refer to Figure 5-12 for the write sequence.

For a single byte write, the master sends a STOP or

RESTART condition after the 1st data byte is sent.

The MSb of each Data Byte is a don’t care, since the

wiper register is only 7-bits wide.

Figure 5-14 shows the I2C communication behavior of

the Master Device and the MCP4017/18/19 device and

the resultant I2C bus values.

5.4.2

READ OPERATIONS

The read operation requires the START condition,

Control Byte, Acknowledge, Data Byte, the master

generating the A and STOP condition. The Control

Byte requires the R/W bit equal to a logic one (R/W =

1) to generate a read sequence. The MCP4017/18/19

will A the Slave Address Byte and A all the Data Bytes.

The I2C Master will A the Slave Address Byte and the

last Data Byte. If there are multiple Data Bytes, the I2C

Master will A all Data Bytes except the last Data Byte

(which it will A).

The MCP4017/18/19 maintains control of the SDA

signal until all data bits have been clocked out.

The command is terminated once a Stop (P) condition

occurs. Refer to Figure 5-13 for the read command

sequence. For a single read, the master sends a STOP

or RESTART condition after the 1st data byte (and A

bit) is sent from the slave.

Figure 5-14 shows the I2C communication behavior of

the Master Device and the MCP4017/18/19 device and

the resultant I2C bus values.

FIGURE 5-12:

I2C Write Command Format.

STOP bit

Slave Address Byte

Data Byte

010

S1 1 1

AD2 D1 D0 A

xD6 D5 D4

D2 D1 D0 A

Fixed

Address

Data Byte

AD3

x D6 D5D4

D2D1 D0 A P

Read/Write bit (“0” = Write)

xD6 D5 D4

D3 D2 D1 D0

xD6 D5 D4

S = Start Condition

P = Stop Condition

A = Acknowledge

X = Don’t Care

R/W = Read/Write bit

D6, D5, D4, D3, D2, D1, D0 = Data bits

Legend

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