MCP4728 datasheet(30/66 Pages) MICROCHIP

30 / 66 page

MCP4728

DS22187C-page 30

In this case, the slave (MCP4728) will leave the data

line HIGH to enable the master to generate the STOP

condition.

FIGURE 5-1:

Data Transfer Sequence On The Serial Bus.

5.3

MCP4728 Device Addressing

The address byte is the first byte received following the

START condition from the master device. The first part

of the address byte consists of a 4-bit device code

which is set to 1100 for the MCP4728 device. The

device code is followed by three I2C address bits (A2,

A1, A0) which are programmable by the users.

Although the three address bits are programmable at

the user’s application PCB, the user can also specify

the address bits during the product ordering process. If

there is no user’s request, the factory default setting of

the three address bits is “000” which is programmed

into the EEPROM. The three address bits allows eight

unique addresses.

FIGURE 5-2:

Device Addressing.

5.3.1

PROGRAMMING OF I2C ADDRESS

BITS

When the customer first receives any new MCP4728

device, its default address bit setting is “000” if the

address bit programming was not requested. The

customer can reprogram the I2C address bits into the

EEPROM by using “Write Address Bit” command. This

write command needs current address bits. If the

address bits are unknown, the user can find them by

sending “General Call Read Address” Command. The

LDAC pin is also used to select the device of interest to

be programmed or to read the current address.

The following steps are needed for the I2C address

programming.

(a) Read the address bits using “General Call Read

Address” Command. (This is the case when the

address is unknown.)

(b) Write I2C address bits using “Write I2C Address

Bits” Command.

The write address command will replace the current

address with a new address in both input registers and

EEPROM.

See

Section 5.4.4 “General call Read Address Bits”

for the details of reading the address bits, and

Section 5.6.8 “Write Command: Write I2C Address

bits (C2=0, C1=1, C0=1)” for writing the address bits.

SCL

SDA

(A)

(B)

(D)

(A)

(C)

START

CONDITION

ADDRESS OR

ACKNOWLEDGE

VALID

DATA

ALLOWED

TO CHANGE

STOP

CONDITION

Start bit

Read/Write bit

Address Byte

R/W

ACK

Acknowledge bit

Slave Address

Slave Address for

MCP4728

Note:

Device Code: Programmed (hard-wired) at the factory.

Address Bits: Reprogrammable into EEPROM by the user.

Device Code

Address Bits

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