MAX7326 Maxim, MAX7326 Datasheet - Page 13

• Manufacturer Part Number: MAX7326
• Description: The MAX7326, a 2-wire serial-interfaced peripheral, features 12 push-pull outputs and four input ports with selectable internal pullups and transition detection
• Manufacturer: Maxim

The master can read 2 bytes from the group A ports of the
MAX7326 and then issues a STOP condition
this case, the MAX7326 transmits the current port data,
followed by the transition flags. The transition flags are
then cleared, and transition detection restarts. 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, and
therefore, port transitions occuring during the transmission
are detected. INT remains high until the STOP condition.
A read from the group B ports of the MAX7326 starts
with the master transmitting the group’s slave address
with the R/W bit set high. The MAX7326 acknowledges
the slave address and samples the logic state of the
output ports during the acknowledge bit. The master
can read one or more bytes from the output ports of the
Figure 7. Reading Group A Ports of the MAX7326 (2 Data Bytes)
Figure 8. Reading Group B Ports of the MAX7326
t
IV
S = START CONDITION
P = STOP CONDITION
A = ACKNOWLEDGE
PORTS
INT OUTPUT
I
2
SCL
S
C Port Expander with 12 Push-Pull Outputs
SCL
S
MAX7326 SLAVE ADDRESS
______________________________________________________________________________________
MAX7326 SLAVE ADDRESS
ACKNOWLEDGE FROM MAX7326
ACKNOWLEDGE
FROM MAX7326
R/W
PORT SNAPSHOT DATA
1
A
t
IR
(Figure
t
PH
O7
PORT SNAPSHOT
D7
R/W
INT REMAINS HIGH UNTIL STOP CONDITION
O6
D6
7). In
1
I5
D5
I4
A
D4
PORT SNAPSHOT TAKEN
I3
P7
D7
D3
PORT SNAPSHOT
MAX7326, and then issues a STOP condition
The MAX7326 transmits the current port data, read
back from the actual port outputs (not the port output
latches) during the acknowledge bit. If a port is forced
to a logic state other than its programmed state, the
readback reflects this. If driving a capacitive load, the
readback port level verification algorithms may need to
take the RC rise/fall time into account.
Typically, the master reads one byte from the group B
ports of the MAX7326, then issues a STOP condition
(Figure
bytes from the output ports of the MAX7326, and then
issues a STOP condition. In this case, the MAX7326
resamples the port outputs during each acknowledge
and transmits the new data each time.
I2
D2
P6
D6
S = START CONDITION
P = STOP CONDITION
O1
D1
P5
D5
8). However, the master can read two or more
O0
D0
t
PS
P4
D4
DATA 1
A
F7
D7 D6
P3
PORT SNAPSHOT TAKEN
D3
F6
A = ACKNOWLEDGE
P2
D2
F5
D5
P1
D1
F4
and 4 Inputs
D4
P0
F3
D3
D0
PORT SNAPSHOT
F2
D2
A
F1
D1 D0
ACKNOWLEDGE
FROM MASTER
P
F0
A
ACKNOWLEDGE
FROM MASTER
(Figure
FLAG
t
IP
P
8).
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