Digital Potentiometers

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11

Message Format for Writing

A write to the MAX5417/MAX5418/MAX5419 consists of

the transmission of the device’s slave address with the

8th bit set to zero, followed by at least 1 byte of infor-

mation (Figure 7). 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 MAX5417/MAX5418/MAX5419 as

selected by the command byte (Figure 8).

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

volatile memory registers (see Table 2).

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 memo-

ry register. The wiper position is unchanged.

NVREGxVREG: Data transfers from the nonvolatile

memory register to the volatile memory register (wiper

position updates).

VREGxNVREG: Data transfers from the volatile memo-

ry register into the nonvolatile memory register.

A

0

SLAVE ADDRESS

CONTROL BYTE

DATA BYTE

ACKNOWLEDGE FROM

MAX5417/MAX5418/MAX5419

NOP/W

1 BYTE

ACKNOWLEDGE FROM

MAX5417/MAX5418/MAX5419

ACKNOWLEDGE FROM

MAX5417/MAX5418/MAX5419

D15

D14 D13 D12 D11 D10

D9

D8

D1

D0

D3

D2

D5

D4

D7

D6

HOW CONTROL BYTE AND DATA BYTE MAP INTO

MAX5417/MAX5418/MAX5419 REGISTERS

S

A

A

P

S

A

0

SLAVE ADDRESS

CONTROL BYTE

ACKNOWLEDGE FROM

MAX5417/MAX5418/MAX5419

NOP/W

ACKNOWLEDGE FROM

MAX5417/MAX5418/MAX5419

D15

D14

D13

D12

D11

D10

D9

D8

CONTROL BYTE IS STORED ON RECEIPT OF STOP CONDITION

AP

Figure 7. Command Byte Received

Figure 8. Command and Single Data Byte Received