Datasheet

Slave Address
The MAX7322 has a 7-bit-long slave address (Figure 5).
The eighth 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 first (A6), second (A5), and third (A4) bits of the
MAX7322 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 MAX7322 has 16
possible slave addresses (Table 2), allowing up to 16
MAX7322 devices on an I
2
C bus.
Accessing the MAX7322
The MAX7322 is accessed through an I
2
C interface.
The transition flags are cleared, and INT is
deasserted each time the device acknowledges the I
2
C slave
address.
A single-byte read from the MAX7322 returns the status
of the four input ports and the four output ports (read back
as inputs).
A 2-byte read returns the status of the four input ports and
the four output ports (as for a single-byte read), followed
by the transition flags for the four input ports.
A multibyte read (more than 2 bytes before the I
2
C
STOP bit) repeatedly returns the port data, alternating
with the transition flags. As the 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 ports.
If a port data change occurs during the read sequence,
INT is reasserted after the I
2
C STOP bit. The MAX7322
does not generate another interrupt during a single-byte
or multibyte read.
Port data is sampled during the preceding I
2
C
acknowledge bit (the acknowledge bit for the I
2
C slave
address in the case of a single-byte or 2-byte read).
A single-byte write to the MAX7322 sets the logic state
of the four output ports and the 4-bit interrupt mask
resistor, and clears both the internal transition flags and
the INT output when the device acknowledges the slave
address byte.
A multibyte write to the MAX7322 repeatedly sets the
logic state of the four output ports and the 4-bit interrupt
mask register.
Figure 5. Slave Address
SDA
SCL
1 1
A3
A2 A1 A0
0
R/W
MSB
LSB
ACK
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Maxim Integrated │ 11
MAX7322 I
2
C Port Expander with
4 Push-Pull Outputs and 4 Inputs