MAX7323AEE+T Datasheet MAX7323AEE+, MAX7323ATE+, MAX7323AEE+T | P10-P12

MAX7323

Accessing the MAX7323

The MAX7323 is accessed through an I

C interface. The

transition flags are cleared, and INT is deasserted each

time the device acknowledges the I

C slave address.

A single-byte read from the MAX7323 returns the sta-

tus of the four I/O ports and the four output ports (read

back as inputs).

A 2-byte read returns first the status of the four I/O ports

and the four output ports (as for a single-byte read), fol-

lowed by the four transition flags for the four I/O ports.

A multibyte read (more than 2 bytes before the I

STOP bit) repeatedly returns the 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 I/O ports.

If a port data change occurs during the read sequence,

INT is reasserted after the I

C STOP bit. The MAX7323

does not generate another interrupt during a single-

byte or multibyte read.

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 MAX7323 sets the logic state

of the four open-drain I/O ports and four push-pull

outputs.

In a 2-byte write to the MAX7323, the first byte sets the

logic state of the four open-drain I/O ports and four

push-pull outputs, while the second byte sets the inter-

rupt mask bits for the four open-drain I/O ports.

Reading from the MAX7323

A read from the MAX7323 starts with the master trans-

mitting the MAX7323’s slave address with the R/W bit

set high. The MAX7323 acknowledges the slave

address, and samples the ports during the acknowl-

edge bit. INT deasserts during the slave address

acknowledge.

Typically, the master reads 1 or 2 bytes from the

MAX7323, each byte being acknowledged by the mas-

ter upon reception, with the exception of the last byte.

When the master reads 1 byte from the MAX7323 it

subsequently issues a STOP condition (Figure 6).

The MAX7323 transmits the current port data, clears

the change flags, and resets the transition detection.

INT deasserts during the slave acknowledge. The new

snapshot data is the current input port data transmitted

to the master, so any input port changes that occur dur-

ing the transmission are detected. INT remains high

until the STOP condition.

The master can read 2 bytes from the MAX7323 and

then issues a STOP condition (Figure 7). In this case, the

MAX7323 transmits the current port data, followed by the

change flags. The change flags are cleared, and transi-

tion detection restarted. INT goes high (high impedance

if an external pullup resistor is not fitted) during the slave

acknowledge. The new snapshot data is the current port

data transmitted to the master, so any port changes

occurring during the transmission are detected. INT

remains high until the STOP condition.

C Port Expander with 4 Push-Pull Outputs

and 4 Open-Drain I/Os

10 ______________________________________________________________________________________

SDA

SCL

DATA LINE STABLE;

DATA VALID

CHANGE OF DATA

ALLOWED

Figure 3. Bit Transfer

SCL

SDA BY

TRANSMITTER

CLOCK PULSE

FOR ACKNOWLEDGMENT

START

CONDITION

SDA BY

RECEIVER

12 89

Figure 4. Acknowledge

MAX7323

C Port Expander with 4 Push-Pull Outputs

and 4 Open-Drain I/Os

______________________________________________________________________________________ 11

SDA

SCL

A2 A1 A0

R/W

MSB

LSB

ACK

Figure 5. Slave Address

SCL

MAX7321 SLAVE ADDRESS

S1 1 0 A

PORT I/O

P2P3P4P5

D0D1D2D3D4D5D6D7

PORT I/O

INT OUTPUT

R/W

PORT SNAPSHOT

PSU

INT REMAINS HIGH UNTIL STOP CONDITION

DATA

Figure 6. Reading the MAX7323 (1 Data Byte)

SCL

MAX7321 SLAVE ADDRESSS110

PORTS

INT OUTPUT

R/W

PORT SNAPSHOT

AD0D1D2D3D4D5D6D7

PORT SNAPSHOT

PSU

D7 D6 D5 D4 D3 D2 D1 D0 N

PORT SNAPSHOT

INT REMAINS HIGH UNTIL STOP CONDITION

S = START CONDITION

P = STOP CONDITION

SHADED = SLAVE TRANSMISSION

A = ACKNOWLEDGE

N = NOT ACKNOWLEDGE

P2P3P4P5

F2F3F4F5

PORT I/O INTERRUPT FLAGS

Figure 7. Reading the MAX7323 (2 Data Bytes)

MAX7323

Writing to the MAX7323

A write to the MAX7323 starts with the master transmit-

ting the MAX7323’s slave address with the R/W bit set

low. The MAX7323 acknowledges the slave address,

and samples the input ports during acknowledge. INT

goes high (high impedance if an external pullup resistor

is not fitted) during the slave acknowledge. The master

can now transmit 1 or more bytes of data. The MAX7323

acknowledges these subsequent bytes of data and

updates the interrupt mask register with each new byte

until the master issues a STOP condition (Figure 8).

Applications Information

Port Input and I

C Interface Level

Translation from Higher or Lower

Logic Voltages

The MAX7323’s SDA, SCL, AD0, AD2, RST, INT, and

P2–P5 are overvoltage protected to +6V independent of

V+. This allows the MAX7323 to operate from a lower

supply voltage, such as +3.3V, while the I

C interface

and/or some of the four I/O ports are driven from a

higher logic level, such as +5V.

The MAX7323 can operate from a higher supply volt-

age, such as +3V, while the I

C interface and/or some

of the four I/O ports P2–P5 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

MAX7323 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 MAX7323 inputs from

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

higher supply to ensure a high logic voltage greater

than 0.7 x V+.

Port-Output Port-Level Translation

The open-drain output architecture allows for level

translation to higher or lower voltages than the

MAX7323’s supply. Use an external pullup resistor on

any output to convert the high-impedance logic-high

condition to a positive voltage level. The resistor can

be connected to any voltage up to +6V, and the resis-

tor value chosen to ensure no more than 20mA is sunk

in the logic-low condition. For interfacing CMOS inputs,

a pullup resistor value of 220kΩ is a good starting

point. Use a lower resistance to improve noise immuni-

ty, in applications where power consumption is less

critical, or where a faster rise time is needed for a given

capacitive load.

Each of the four output ports O0, O1, O6, and O7 has

protection diodes to GND (Figure 9). When a port is dri-

ven to a voltage lower than GND, the protection diode

clamps the output to a diode drop below GND.

Each of the four I/O ports P2–P5 also has a 40kΩ (typ)

pullup resistor that can be enabled or disabled. When a

port 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 MAX7323 is

powered down (V+ = 0), each I/O port appears as a

40kΩ resistor in series with a diode connected to zero.

Each port is protected to +6V under any of these

circumstances (Figure 10).

C Port Expander with 4 Push-Pull Outputs

and 4 Open-Drain I/Os

12 ______________________________________________________________________________________

SCL

SDA

START CONDITION R/W

SLAVE ADDRESS

12345678

AAA

DATA 1 DATA 2

DATA TO PORT DATA TO PORT

DATA 2 VALIDDATA 1 VALID

INTERNAL WRITE

TO PORT

DATA OUT

FROM PORT

S = START CONDITION SHADED = SLAVE TRANSMISSION

P = STOP CONDITION N = NOT ACKNOWLEDGE

Figure 8. Writing to the MAX7323

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P17

MAX7323AEE+T

Mfr. #:

Buy MAX7323AEE+T

Manufacturer:

Maxim Integrated

Description:

Interface - I/O Expanders I2C Port Expander w/4 P-P Out & 4 I/O

Lifecycle:

New from this manufacturer.

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MAX7323AEE+T

MAX7323AEE+T

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