MAX7322 Maxim, MAX7322 Datasheet - Page 12

• Manufacturer Part Number: MAX7322
• Description: The MAX7322 2-wire serial-interfaced peripheral features four push-pull outputs and four input ports with selectable internal pullups
• Manufacturer: Maxim

I
4 Push-Pull Outputs and 4 Inputs
A read from the MAX7322 starts with the master trans-
mitting the MAX7322’s slave address with the R/W bit
set high. The MAX7322 acknowledges the slave
address, and samples the ports during the acknowl-
edge 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 mas-
ter 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),
Figure 6. Reading from the MAX7322 (1 Data Byte)
Figure 7. Reading from the MAX7322 (2 Data Bytes)
12
2
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
N = NOT ACKNOWLEDGE
C Port Expander with
______________________________________________________________________________________
t
IV
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
N = NOT ACKNOWLEDGE
PORTS
INT OUTPUT
t
IV
SCL
S
PORTS
INT OUTPUT
1
S
SCL
1
1
0
MAX7322 SLAVE ADDRESS
Reading from the MAX7322
1
0
MAX7322 SLAVE ADDRESS
R/W
1
A
t
IR
t
PH
PORT SNAPSHOT
O7
D7
INT REMAINS HIGH UNTIL STOP CONDITION
R/W
O6
D6
I5
1
D5
PORT INPUTS
I4
D4
A
I3
t
IR
t
D3
PH
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 trans-
mitted 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
PORT SNAPSHOT
O7
PORT SNAPSHOT
D7
I2
D2
O6
INT REMAINS HIGH UNTIL STOP CONDITION
I1
D6
D1
I5
O0
t
PSU
D0
D5
I4
PORTS
A
D4
0
D7
I3
D3
0
D6
I2
INTERRUPT FLAGS
F5
D5
D2
PORT SNAPSHOT
F4
O1
D4
D1
F3
D3
O0
PORT SNAPSHOT
D0
F2
D2
ACKNOWLEDGE
FROM MAX7322
t
PSU
0
D1 D0
N
0
P
ACKNOWLEDGE
FROM MAX7322
N
t
IP
t
P
IP