Any of the four open-drain ports can be configured as a

logic input by setting the port output logic-high (logic-

high for an open-drain output is high impedance).

When the MAX7323 is read through the serial interface,

the actual logic levels at the ports are read back.

The four ports offer latching transition detection func-

tionality. All input ports are continuously monitored for

changes. An input change sets 1 of 4 flag bits that

identify changed input(s). All flags are cleared upon a

subsequent read or write transaction to the MAX7323.

A latching interrupt output, INT, automatically flags data

changes on any of the I/O ports used as inputs. The

interrupt output INT, and all transition flags are

deasserted when the MAX7323 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 two (see Table 3).

Use the slave address selection to ensure that I/O ports

used as inputs are logic-high on power-up. I/O ports with

internal pullups enabled default to a logic-high output

state. I/O ports with internal pullups disabled default to

a logic-low output state. Output port power-up logic

states are selected by the address select inputs AD0

and AD2. Ports default to logic-high or logic-low on

power-up in groups of two (see Table 3).

Initial Power-Up

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

INT is deasserted. The interrupt mask register is set to

0x3C, enabling the interrupt output for transitions on all

four input ports. The transition flags are cleared to indi-

cate no data changes. The power-up default state of the

address selection inputs, AD0 and AD2 (see Table 3).

Power-On Reset

The MAX7323 contains an integral power-on-reset

(POR) circuit that ensures all registers are reset to a

(1.6V max), the POR circuit releases the registers and

2-wire interface for normal operation. When V+ drops to

POR defaults (see Table 3).

RST Input

The active-low RST input operates as a reset that voids

reset action does not clear the interrupt output (INT).

Standby Mode

When the serial interface is idle, the MAX7323 automat-

ically enters standby mode, drawing minimal supply

current.

and 4 Open-Drain I/Os

6

_______________________________________________________________________________________

PART

SLAVE

ADDRESS

INPUTS

INPUT

INTERRUPT

MASK

OPEN-

DRAIN

OUTPUTS

PUSH-

PULL

OUTPUTS

APPLICATION

MAX7323

110xxxx

Up to 4

—

Up to 4

4

4 I/O, 4 output-only versions:

4 open-drain I/O ports with latching transition

detection interrupt and selectable pullups.

4 push-pull outputs with selectable power-up default

levels.

MAX7328

MAX7329

0100xxx

0111xxx

Up to 8

—

Up to 8

—

8 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.

16-PORT EXPANDERS

MAX7324

8

Yes

—

8

Software equivalent to a MAX7320 plus a MAX7319.

MAX7325

Up to 8

—

Up to 8

8

Software equivalent to a MAX7320 plus a MAX7321.

MAX7326

4

Yes

—

12

Software equivalent to a MAX7320 plus a MAX7322.

MAX7327

101xxxx

and

110xxxx

Up to 4

—

Up to 4

12

Software equivalent to a MAX7320 plus a MAX7323.

Table 1. MAX7319–MAX7329 Family Comparison (continued)