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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

Slave Address

The MAX7319 has a 7-bit slave address (Figure 5). The

8th bit following the 7-bit slave address is the R/W bit. It

is low for a write command, and high for a read

command.

The 1st (A6), 2nd (A5), and 3rd (A4) bits of the MAX7319

slave address are always 1, 1, and 0. Connect AD2 and

AD0 to GND, V+, SDA, or SCL to select slave address

bits A3, A2, A1, and A0. The MAX7319 has 16 possible

slave addresses (Table 3), allowing up to 16 MAX7319

devices on an I2C bus

Accessing the MAX7319

I2C-interface access to the MAX7319 is summarized as

follows (Table 2):

A single-byte read from the MAX7319 returns the

status of the eight input ports, and clears both the internal

transition flags and the INT output (Figure 7).

A 2-byte read returns the status of the eight input ports

(as for a single-byte read), followed by the transition

flags. The internal transition flags and the INT output

are cleared when the MAX7319 acknowledges the

slave address byte, but the previous transition flag data

is sent as the second byte (Figure 8).

A multibyte read (more than 2 bytes before the I2C

STOP bit) repeatedly returns the input port data,

alternating with the transition flags. As the input data is

resampled for each transmission, and the transition

flags are reset each time, a multibyte read continuously

returns the current data and identifies any changing

input ports.

If a port input data change occurs during the read

sequence, INT is reasserted after the I2C STOP bit. The

MAX7319 does not generate another interrupt during a

single-byte or multibyte read.

SDA

1

1

MSB

SCL

Figure 5. Slave Address

0

A3

A2

A1

A0

R/W

ACK

LSB

PORT INPUTS

I7 I6 I5 I4 I3 I2 I1 I0

S 1 1 0 MAX7319 SLAVE ADDRESS 1 A D7 D6 D5 D4 D3 D2 D1 D0 N P

R/W

PORT SNAPSHOT

PORT SNAPSHOT

SCL

PORT INPUT

tIV

INT OUTPUT

tPH

tIR

tPSU

tIP

INT REMAINS HIGH UNTIL STOP CONDITION

Figure 6. Reading from the MAX7319 (1 Data Byte)

S = START CONDITION

P = STOP CONDITION

SHADED = SLAVE TRANSMISSION

N = NOT ACKNOWLEDGE

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