MAX7323 Maxim, MAX7323 Datasheet - Page 8

• Manufacturer Part Number: MAX7323
• Description: The MAX7323 2-wire serial-interfaced peripheral features eight I/O ports
• Manufacturer: Maxim

I
and 4 Open-Drain I/Os
and AD0 to V+ or GND (shown in bold in Table 3).
These selections are guaranteed to be correct at
power-up, independent of SDA and SCL behavior. If
one of the other 12 address combinations is used, an
unexpected combination of pullups might be asserted
until the first I
sarily the MAX7323) is put on the bus.
I/O port inputs switch at the CMOS logic levels as
determined by the expander’s supply voltage, and are
overvoltage tolerant to +6V, independent of the
expander’s supply voltage.
All four I/O ports configured as inputs are monitored for
changes since the expander was last accessed
through the serial interface. The state of the I/O ports is
stored in an internal “snapshot” register for transition
monitoring. The snapshot is continuously compared
with the actual input conditions, and if a change is
detected for any port input, INT is asserted to signal a
state change. An internal transition flag is set for that
port. The input ports are sampled (internally latched
into the snapshot register) and the old transition flags
cleared during the I
read and write access. The previous port transition
Table 3. MAX7323 Address Map
8
CONNECTION
GND
GND
GND
GND
2
AD2
SDA
SDA
SDA
SDA
SCL
SCL
SCL
SCL
V+
V+
V+
V+
_______________________________________________________________________________________
C Port Expander with 4 Push-Pull Outputs
PIN
GND
GND
GND
GND
AD0
SCL
SDA
SCL
SDA
SCL
SDA
SCL
SDA
V+
V+
V+
V+
I/O Port Input Transition Detection
2
C transmission (to any device, not neces-
A6
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
A5 A4 A3 A2 A1 A0 O7 O6 P5
C acknowledge of every MAX7323
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
DEVICE ADDRESS
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
I/O Port Inputs
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
OUTPUTS POWER-UP DEFAULT
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
flags are read through the serial interface as the sec-
ond byte of a 2-byte read sequence.
A long read sequence (more than 2 bytes) can be used
to poll the expander continuously without the overhead
of resending the slave address. If more than 2 bytes
are read from the expander, the expander repeatedly
returns the input port data, alternating with the transition
flags. The inputs are repeatedly resampled and the
transition flags repeatedly reset for each pair of bytes
read. All changes that occur during a long read
sequence are detected and reported.
The INT output is not reasserted during a read
sequence to avoid recursive reentry into an interrupt
service routine. Instead, if a data change occurs that
would normally cause the INT output to be set, the INT
assertion is delayed until the STOP condition. INT is not
reasserted upon a STOP condition if the changed input
data is read before the STOP occurs. The INT logic
ensures that unnecessary interrupts are not asserted,
yet data changes are detected and reported no matter
when the change occurs.
Write 1 byte to the MAX7323 to set the output port lev-
els for the four push-pull outputs, and the four open-
drain I/O ports simultaneously.
P4 P3
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
P2 O1 O0 O7 O6 P5 P4 P3 P2 O1 O0
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
40kΩ INPUT PULLUPS ENABLED
—
—
—
—
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
—
—
—
—
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Port Outputs
—
—
—
—
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
—
—
—
—
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y