MAX7319ATE+T Datasheet MAX7319ATE+T, MAX7319AEE+, MAX7319ATE+ | P10-P12

MAX7319

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 com-

mand.

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 I

C bus

Accessing the MAX7319

C-interface access to the MAX7319 is summarized as

follows (Table 2).

A single-byte read from the MAX7319 returns the sta-

tus 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 I

STOP bit) repeatedly returns the input port data, alter-

nating 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 I

C STOP bit. The

MAX7319 does not generate another interrupt during a

single-byte or multibyte read.

C Port Expander with Eight Inputs and

Maskable Transition Detection

10 ______________________________________________________________________________________

SDA

SCL

A2 A1 A0

R/W

MSB

LSB

ACK

Figure 5. Slave Address

SCL

MAX7319 SLAVE ADDRESS

S1 1 0 A

PORT INPUT

I2I3I4I5

D0D1D2D3D4D5D6D7

PORT INPUTS

INT OUTPUT

R/W

PORT SNAPSHOT

PSU

INT REMAINS HIGH UNTIL STOP CONDITION

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

S = START CONDITION SHADED = SLAVE TRANSMISSION

P = STOP CONDITION N = NOT ACKNOWLEDGE

MAX7319

C Port Expander with Eight Inputs and

Maskable Transition Detection

______________________________________________________________________________________ 11

SCL

MAX7319 SLAVE ADDRESS A011S P1

PORTS

INT OUTPUT

R/W

PORT SNAPSHOT

I2I3I4I5

D0D1D2D3D4D5D6D7

PORT SNAPSHOT

PSU

F2F3F4F5

D7 D6 D5 D4 D3 D2 D1 D0 N

PORT SNAPSHOT

INT REMAINS HIGH UNTIL STOP CONDITION

SGALF TPURRETNISTUPNI TROP

S = START CONDITION SHADED = SLAVE TRANSMISSION

P = STOP CONDITION N = NOT ACKNOWLEDGE

Figure 7. Reading from the MAX7319 (2 Data Bytes)

Input port data is sampled during the preceding I

acknowledge bit (the acknowledge bit for the I

C slave

address in the case of a single-byte or 2-byte read).

A single-byte write to the MAX7319 sets the interrupt

mask register, and clears both the internal transition

flags and the INT output.

A multibyte write to the MAX7319 sets the interrupt

mask register repeatedly.

Reading from the MAX7319

A read from the MAX7319 starts with the master trans-

mitting the MAX7319’s slave address with the R/W bit

set high. The MAX7319 acknowledges the slave

address and samples the input ports during acknowl-

edge bit. INT deasserts during the slave address

acknowledge.

Typically, the master reads 1 or 2 bytes from the

MAX7319, with each byte, except the last one, being

acknowledged by the master upon reception.

When the master reads 1 byte from the MAX7319 and

subsequently issues a STOP condition (Figure 6), the

MAX7319 transmits the current port data, clears the

transition flags, and resets the transition detection. INT

deasserts during the slave address acknowledge. The

new snapshot data is the current port data transmitted

to the master; therefore, port transitions ocurring during

the transmission are detected. INT remains high until

the STOP condition.

When the master reads 2 bytes from the MAX7319 and

subsequently issues a STOP condition (Figure 7), the

MAX7319 transmits the current port data, followed by

the transition flags. The transition flags are cleared, and

transition detection reset. INT deasserts during the

slave address acknowledge. The new snapshot data is

the current port data transmitted to the master; there-

fore, port transitions occurring during the transmission

are detected. INT remains high until the STOP condi-

tion. When the master reads more than 2 bytes, the

input port data alternates with the transition flag.

S = START CONDITION SHADED = SLAVE TRANSMISSION

P = STOP CONDITION N = NOT ACKNOWLEDGE

Writing to the MAX7319

A write to the MAX7319 starts with the master transmit-

ting the MAX7319’s slave address with the R/W bit set

low. The MAX7319 acknowledges the slave address,

and samples the input ports during the acknowledge

bit. INT deasserts during the slave address acknowl-

edge. The master can now transmit 1 or more bytes of

data. The MAX7319 acknowledges these subsequent

bytes of data and updates the interrupt mask register

with each new byte until the master issues a STOP con-

dition (Figure 8).

Applications Information

Port Input and I

C Interface Level

Translation from Higher or Lower

Logic Voltages

The MAX7319 I

C interface (SDA, SCL, AD0, AD2),

reset input RST, interrupt output INT, and the eight

input ports I0–I7 are overvoltage protected to +6V inde-

pendent of V+. This allows the MAX7319 to operate

from a lower supply voltage, such as +3.3V, while the

C interface and/or any of the eight input ports are dri-

ven from a higher logic level, such as +5V.

The MAX7319 can operate from a higher supply volt-

age, such as +3V, while the I

C interface and/or some

of the input ports I0–I7 are driven from a lower logic

level, such as +2.5V. Apply a minimum voltage of 0.7 x

V+ to assert a logic-high on any input. For example, a

MAX7319 operating from a +5V supply may not recog-

nize a +3.3V nominal logic-high. One solution for input

level translation is to drive the MAX7319 inputs from

open-drain outputs. Use a pullup resistor to V+ or a

higher supply to ensure a high logic voltage of greater

than 0.7 x V+.

Hot Insertion

RST, SCL, SDA, AD0, and AD2 remain high impedance

with up to +6V asserted on them when the MAX7319 is

powered down (V+ = 0). The MAX7319 can therefore

be used in hot-swap applications.

Each of the input ports I0–I7 has a protection diode to

GND (Figure 9). When a port input is driven to a voltage

lower than GND, the protection diode clamps the volt-

age to a diode drop below GND.

Each of the input ports I0–I7 also has a 40kΩ (typ)

pullup resistor that can be enabled or disabled. When a

port input is driven to a voltage higher than V+

the

body diode of the pullup enable switch conducts and

the 40kΩ pullup resistor is enabled. When the

MAX7319 is powered down (V+ = 0), every input port

appears as a 40kΩ resistor in series with a diode con-

nected to GND. Input ports are protected to +6V under

any of these circumstances (Figure 9).

MAX7319

C Port Expander with Eight Inputs and

Maskable Transition Detection

12 ______________________________________________________________________________________

I0–I7

PULLUP

ENABLE

INPUT

40kΩ

MAX7319

V+

Figure 9. Input Port Structure

SCL

SDA

START CONDITION R/W

SLAVE ADDRESS

12345678

AAA

DATA 1 DATA 2

DATA TO INTERRUPT MASK DATA TO INTERRUPT MASK

Figure 8. Writing to the MAX7319

S = START CONDITION SHADED = SLAVE TRANSMISSION

P = STOP CONDITION N = NOT ACKNOWLEDGE

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P16

MAX7319ATE+T

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Interface - I/O Expanders I2C Port Expander 8 Input

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MAX7319ATE+T

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