Digital Potentiometers

______________________________________________________________________________________

13

3 bits in the slave address. Connect each address input

have a unique address to share a common bus.

Message Format for Writing

Write to the MAX5477/MAX5478/MAX5479 by transmit-

ting the device’s slave address with NOP/W (8th bit) set

to zero, followed by at least 1 byte of information

byte. The bytes received after the command byte are

the data bytes. The 1st data byte goes into the internal

register of the MAX5477/MAX5478/MAX5479 as select-

Command Byte

Use the command byte to select the source and desti-

nation of the wiper data (nonvolatile or volatile memory

registers) and swap data between nonvolatile and

Command Descriptions

VREG: The data byte writes to the volatile memory reg-

ister and the wiper position updates with the data in the

volatile memory register.

NVREG: The data byte writes to the nonvolatile memory

register. The wiper position is unchanged.

NVREGxVREG: Data transfers from the nonvolatile

memory register to the volatile memory register (wiper

position updates).

SDA

DATA STABLE,

DATA VALID

CHANGE OF

DATA ALLOWED

SCL

Figure 5. Bit Transfer

1

SCL

START

CONDITION

SDA

28

9

CLOCK PULSE FOR

ACKNOWLEDGMENT

ACKNOWLEDGE

NOT ACKNOWLEDGE

Figure 6. Acknowledge

A

0

SLAVE ADDRESS

COMMAND BYTE

DATA BYTE

ACKNOWLEDGE FROM

MAX5477/MAX5478/MAX5479

NOP/W

1 BYTE

ACKNOWLEDGE FROM

MAX5477/MAX5478/MAX5479

ACKNOWLEDGE FROM

MAX5477/MAX5478/MAX5479

D15

D14 D13 D12 D11 D10

D9

D8

D1

D0

D3

D2

D5

D4

D7

D6

HOW CONTROL BYTE AND DATA BYTE MAP INTO

MAX5477/MAX5478/MAX5479 REGISTERS

S

A

A

P

S

A

0

SLAVE ADDRESS

COMMAND BYTE

ACKNOWLEDGE FROM

MAX5477/MAX5478/MAX5479

NOP/W

ACKNOWLEDGE FROM

MAX5477/MAX5478/MAX5479

D15

D14

D13

D12

D11

D10

D9

D8

COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION

AP

Figure 7. Command Byte Received

Figure 8. Command and Single Data Byte Received