Potentiometers

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high while SCL is high. The bus is then free for another

transmission (Figure 3).

Bit Transfer

One data bit is transferred during each clock pulse.

The data on the SDA line must remain stable while SCL

is high (Figure 5).

Acknowledge

The acknowledge bit is a clocked 9th bit that the recip-

ient uses to handshake receipt of each byte of data

(Figure 6). Each byte transferred effectively requires 9

bits. The master generates the 9th clock pulse, and the

recipient pulls down SDA during the acknowledge

clock pulse, so the SDA line is stable low during the

high period of the clock pulse. When the master trans-

mits to the MAX5432–MAX5435, the devices generate

the acknowledge bit because the MAX5432–MAX5435

are the recipients.

Slave Address

The MAX5432–MAX5435 have a 7-bit-long slave

address (Figure 4). The 8th bit following the 7-bit slave

address is the NOP/W bit. Set the NOP/W bit low for a

write command and high for a no-operation command.

Table 1a shows four possible slave addresses for the

MAX5432/MAX5433 and Table 1b shows four possible

slave addresses for the MAX5434/MAX5435. The first 4

bits (MSBs) of the slave addresses are always 0101.

Bits A2 and A1 are factory programmed for the

MAX5432/MAX5433 (Table 1a). Connect the A0 input

must have a unique address to share the bus. A maxi-

mum of four MAX5432/MAX5433 devices can share the

same bus. Bits A2, A1, and A0 are factory programmed

for the MAX5434/MAX5435 (Table 1b).

Message Format for Writing

A write to the MAX5432–MAX5435 consists of the trans-

mission of the device’s slave address with the 8th bit set

to zero, followed by at least 1 byte of information. The

1st byte of information is the command byte. The bytes

received after the command byte are the data bytes.

The 1st data byte goes into the internal register of the

MAX5432–MAX5435 as selected by the command byte

(Figure 8).

S

Sr

A

PS

SCL

SDA

PARAMETERS ARE MEASURED FROM 30% TO 70%.

ADDRESS BYTE

PART

SUFFIX

A6

A5

A4

A3

A2

A1

A0

NOP/W

L

0

1

0

1

0

0

0

NOP/W

M

0

1

0

1

1

0

0

NOP/W

N

0

1

0

1

0

1

0

NOP/W

P

0

1

0

1

1

1

0

NOP/W

ADDRESS BYTE

PART

SUFFIX

A6

A5

A4

A3

A2

A1

A0

NOP/W

L

0101000

NOP/W

L

0101001

NOP/W

M

0101100

NOP/W

M

0101101

NOP/W

Table 1a. Address Codes

(MAX5432/MAX5433 Only)

Table 1b. Address Codes

(MAX5434/MAX5435 Only)