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MAX7319

I2C Port Expander with Eight Inputs and Maskable Transition Detection

Maxim Integrated 

MAX7319

I2C Port Expander with Eight Inputs

and Maskable Transition Detection

Table 1. MAX7319–MAX7329 Family Comparison (continued)

PART

I2C

INPUT

SLAVE INPUTS INTERRUPT

ADDRESS

MASK

OPEN-

DRAIN

OUTPUTS

MAX7323 110xxxx Up to 4

—

Up to 4

MAX7328

MAX7329

0100xxx

0111xxx

Up to 8

—

16-PORT EXPANDERS

MAX7324

8

Yes

MAX7325 101xxxx Up to 8

—

MAX7326

And

110xxxx

4

Yes

MAX7327

Up to 4

—

Up to 8

—

Up to 8

—

Up to 4

PUSH-

PULL

OUTPUTS

APPLICATION

Four I/O, four output-only versions:

Four open-drain I/O ports with latching transition

4

detection interrupt and selectable pullups.

Four push-pull outputs with selectable power-up

default levels.

PCF8574-, PCF8574A-compatible versions:

Eight open-drain I/O ports with nonlatching transition

—

detection interrupt and pullups on all ports.

All ports power up as inputs (or logic-high outputs).

Any port can be used as an input by setting the

open-drain output to logic-high.

8

Software equivalent to a MAX7320 plus a MAX7321.

8

Software equivalent to a MAX7320 plus a MAX7319.

12

Software equivalent to a MAX7320 plus a MAX7322.

12

Software equivalent to a MAX7320 plus a MAX7323.

for changes. An input change sets one of eight flag bits

that identify changed input(s). All flags are cleared

upon a subsequent read or write transaction to the

MAX7319.

A latching interrupt output, INT, is programmed to flag

input data changes on input ports through an interrupt

mask register. By default, data changes on any input

port force INT to a logic-low. The interrupt output, INT,

and all transition flags are cleared when the MAX7319

is next accessed through the serial interface.

Internal pullup resistors to V+ are selected by the

address-select inputs, AD0 and AD2. Pullups are enabled

on the input ports in groups of four (see Table 3).

Initial Power-Up

On power-up, the transition detection logic is reset, and

INT is released to a high-impedance state. The interrupt

mask register is set to 0xFF, enabling the interrupt output

for transitions on all eight input ports. The transition flags

are cleared to indicate no data changes.

RST Input

The RST input voids any I2C transaction involving the

MAX7319, forcing the MAX7319 into the I2C STOP

condition. A reset does not affect the interrupt output (INT)

or change the contents of the interrupt mask register.

RST is overvoltage tolerant to +6V.

Standby Mode

When the serial interface is idle, the MAX7319

automatically enters standby mode, drawing minimal

supply current.

Slave Address and Input Pullup Selection

Address inputs AD0 and AD2 determine the MAX7319

slave address and select which inputs have pullup

resistors. Pullups are enabled on the input ports in

groups of four (see Table 3). The MAX7319, MAX7321,

MAX7322, and MAX7323 use a different range of slave

addresses (110xxxx) than the MAX7320 (101xxxx).

The MAX7319 slave address is determined on each I2C

transmission, regardless of whether the transmission is

actually addressing the MAX7319. The MAX7319

distinguishes whether address inputs AD2 and AD0 are

connected to SDA or SCL instead of fixed logic levels

V+ or GND during this transmission. This means that the

MAX7319 slave address can be configured dynamically

in the application without cycling the device supply.

On initial power-up, the MAX7319 cannot decode the

address inputs AD2 and AD0 fully until the first I2C

transmission. AD0 and AD2 initially appear to be con-

nected to V+ or GND. This is important because the

address selection determines which inputs have

pullups applied. However, at power-up, the I2C SDA

and SCL bus interface lines are high impedance at the

pins of every device (master or slave) connected to the

bus, including the MAX7319. This is guaranteed as part

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