Datasheet
Reading from the MAX7322
A read from the MAX7322 starts with the master
transmitting the MAX7322’s slave address with the R/W
bit set high. The MAX7322 acknowledges the slave
address, and samples the ports during the
acknowledge bit. INT deasserts during the slave address
acknowledge.
Typically, the master reads one or two bytes from
the MAX7322, each byte being acknowledged by the
master upon reception with the exception of the last byte.
When the master reads one byte from the MAX7322
and subsequently issues a STOP condition (Figure 6),
the MAX7322 transmits the current port data, clears
the change flags, and restarts the transition detection.
INT deasserts during the slave address acknowledge.
The new snapshot data is the current input port data
transmitted to the master, so any input port changes that
occur during the transmission are detected. INT remains
high until the STOP condition.
The master can read two bytes from the MAX7322 and
then issue a STOP condition (Figure 7). In this case, the
MAX7322 transmits the current port data, followed by
the change flags. The change flags are then cleared,
and transition detection restarts. INT deasserts during
the slave address acknowledge. The new snapshot
Figure 6. Reading from the MAX7322 (1 Data Byte)
Figure 7. Reading from the MAX7322 (2 Data Bytes)
SCL
MAX7322 SLAVE ADDRESSS 1 1 0
A
P
1
PORTS
INT OUTPUT
R/W
PORT SNAPSHOT
t
IV
t
PH
t
IR
AD0D1D2D3D4D5D6D7
PORT SNAPSHOT
t
PSU
t
IP
D7 D6 D5 D4 D3 D2 D1 D0
ACKNOWLEDGE
FROM MAX7322
N
PORT SNAPSHOT
INT REMAINS HIGH UNTIL STOP CONDITION
O0
I1
I2I3I4I5
O6
O7
0
0
F2F3F4F5
0
0
PORT INPUTS INTERRUPT FLAGS
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
N = NOT ACKNOWLEDGE
SCL
MAX7322 SLAVE ADDRESS
S
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
N = NOT ACKNOWLEDGE
1 1 0 A
P
1
PORTS
t
IV
N
O0
O1
I2I3I4I5
O6
O7
D0D1D2D3D4D5D6D7
PORTS
INT OUTPUT
R/W
PORT SNAPSHOT
t
PH
t
IR
PORT SNAPSHOT
t
PSU
t
IP
INT REMAINS HIGH UNTIL STOP CONDITION
ACKNOWLEDGE
FROM MAX7322
www.maximintegrated.com
Maxim Integrated
│
12
MAX7322 I
2
C Port Expander with
4 Push-Pull Outputs and 4 Inputs