MCP40D18 datasheet(38/66 Pages) MICROCHIP

38 / 66 page

MCP40D17/18/19

DS22152B-page 38

5.4.1

WRITE OPERATION

The write operation requires the START condition,

Control

Byte,

Acknowledge,

Command

Code,

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 MCP40D17/

18/19 is responsible for generating the Acknowledge

(A) bits.

Data is written to the MCP40D17/18/19 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 MCP40D17/18/

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 single byte write

sequence and Figure 5-13 for the generic (multi-byte)

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.

The command is terminated once a Stop (P) or Restart

(S) condition occurs.

Figure 5-14 shows the I2C write communication

behavior of the Master Device and the MCP40D17/18/

19 device and the resultant I2C bus values.

5.4.2

READ OPERATIONS

The read operation requires the START condition,

Control

Byte,

Acknowledge,

Command

Code,

Acknowledge,

Restart

Condition,

Control

Byte,

Acknowledge, Data Byte, the master generating the

A and STOP (or RESTART) condition. The first Control

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

“0”

) to write the Command Code, while the second

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

(R/W = “1”) to generate a read sequence. The

MCP40D17/18/19 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 MCP40D17/18/19 maintains control of the SDA

signal until all data bits have been clocked out.

The command is terminated once a Stop (P) or Restart

(S) condition occurs. Refer to Figure 5-15 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 5-16 shows the I2C read communication

behavior of the Master Device and the MCP40D17/18/

19 device and the resultant I2C bus values.

FIGURE 5-12:

I2C Single Byte Write Command Format (Slave Address = “0101110”).

Note:

A command code with a non-zero value

will cause the data not to be written to the

wiper register

Note:

A command code with a non-zero value

will cause the data not to be read from the

wiper register

STOP bit

Slave Address Byte

Command Code

Data Byte

010

X D6 D5D4

D2D1 D0 A

Fixed

Address

Read/Write bit (“0” = Write)

S = Start Condition

P = Stop Condition

A = Acknowledge

X = Don’t Care

R/W = Read/Write bit

D6:D0 = Data bits

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