MAX5479 Maxim, MAX5479 Datasheet - Page 11

• Manufacturer Part Number: MAX5479
• Description: Dual - 256-Tap/ Nonvolatile/ I2C-Interface/ Digital Potentiometers
• Manufacturer: Maxim

slave address is the NOP/W bit. Set the NOP/W bit low for
a write command and high for a no-operation command.
The MAX5477/MAX5478/MAX5479 provide three
address inputs (A0, A1, and A2), allowing up to eight
devices to share a common bus (Table 1). The first 4
bits (MSBs) of the MAX5477/MAX5478/MAX5479 slave
addresses are always 0101. A2, A1, and A0 set the next
3 bits in the slave address. Connect each address input
to V
have a unique address to share a common bus.
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
(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 MAX5477/MAX5478/MAX5479 as select-
ed by the command byte (Figure 8).
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).
VREG: The data byte writes to the volatile memory reg-
ister and the wiper position updates with the data in the
volatile memory register.
Figure 7. Command Byte Received
Figure 8. Command and Single Data Byte Received
S
DD
HOW CONTROL BYTE AND DATA BYTE MAP INTO
or GND to set these 3 bits. Each device must
S
MAX5477/MAX5478/MAX5479 REGISTERS
SLAVE ADDRESS
COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION
Dual, 256-Tap, Nonvolatile, I
MAX5477/MAX5478/MAX5479
______________________________________________________________________________________
Message Format for Writing
ACKNOWLEDGE FROM
SLAVE ADDRESS
NOP/W
Command Descriptions
MAX5477/MAX5478/MAX5479
0
ACKNOWLEDGE FROM
A
Command Byte
D15 D14 D13 D12 D11 D10
NOP/W
0
MAX5477/MAX5478/MAX5479
COMMAND BYTE
ACKNOWLEDGE FROM
A
D15
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).
VREGxNVREG: Data transfers from the volatile memory
register into the nonvolatile memory register.
The internal EEPROM consists of a 16-bit nonvolatile
register that retains the value written to it prior to power
down. The nonvolatile register is programmed with the
midscale value at the factory. The nonvolatile memory
is guaranteed for 50 years for wiper position retention
and up to 200,000 wiper write cycles. A write-protect
feature prevents accidental overwriting of the EEPROM.
Connect WP to V
protect feature. The wiper position only updates with
the value in the EEPROM when WP = V
to GND to allow EEPROM write cycles and to update
the wiper position from nonvolatile memory or directly
from the I
Upon power-up, the MAX5477/MAX5478/MAX5479
load the data stored in the nonvolatile memory register
into the volatile memory register, updating the wiper
position with the data stored in the nonvolatile memory
register. This initialization period takes 10µs.
Digital Potentiometers
D14
D9
D13
D8
2
C serial interface.
COMMAND BYTE
A
D12
D7
DD
MAX5477/MAX5478/MAX5479
D11
D6
or leave open to enable the write-
ACKNOWLEDGE FROM
D10
D5
MAX5477/MAX5478/MAX5479
2
C-Interface,
DATA BYTE
D4
1 BYTE
D9
ACKNOWLEDGE FROM
Nonvolatile Memory
D3
D8
w
D2
DD
A
D1
. Connect WP
w
Power-Up
D0
P
A
w
P
11
.
D