MAX7324 Maxim, MAX7324 Datasheet - Page 13

• Manufacturer Part Number: MAX7324
• Description: The MAX7324 2-wire serial-interfaced peripheral features 16 I/O ports that are divided into eight push-pull outputs and eight inputs
• Manufacturer: Maxim

When the master reads 2 bytes from the output ports of
the MAX7324 and subsequently issues a STOP condi-
tion (Figure 7), the MAX7324 transmits the current port
data, followed by the transition flags. The transition
flags are then cleared, and transition detection is reset.
INT deasserts 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. When the master reads more than
2 data bytes, the input port data alternates with the
transition flag.
A read from the output ports of the MAX7324 starts with
the master transmitting the ports’ slave address with
the R/W bit set high. The MAX7324 acknowledges the
slave address and samples the logic state of the output
ports during the acknowledge bit. The master can read
Figure 7. Reading Input Ports of the MAX7324 (2 Data Bytes)
Figure 8. Reading Output Ports of the MAX7324
I
2
t
IV
C Port Expander with Eight Push-Pull Outputs
PORTS
INT OUTPUT
SCL
S
SCL
S
MAX7324 SLAVE ADDRESS
______________________________________________________________________________________
MAX7324 SLAVE ADDRESS
ACKNOWLEDGE FROM MAX7324
FROM MAX7324
ACKNOWLEDGE
R/W
PORT SNAPSHOT DATA
1
A
t
IR
t
R/W
PH
I7
PORT SNAPSHOT
D7
INT REMAINS HIGH UNTIL STOP CONDITION
I6
1
D6
I5
D5
A
I4
D4
PORT SNAPSHOT TAKEN
P7
D7
I3
D3
PORT SNAPSHOT
P6
one or more bytes from the output ports of the
MAX7324, and then issues a STOP condition (Figure 8).
The MAX7324 transmits the current port data, read
back from the actual port outputs (not the port output
latches) during the acknowledge. If a port is forced to a
logic state other than its programmed state, the read-
back reflects this. If driving a capacitive load, the read-
back port level verification algorithms may need to take
the RC rise/fall time into account.
Typically, the master reads one byte from the ouput
ports of the MAX7324, then issues a STOP condition
(Figure 8). However, the master can read two or more
bytes from the output ports of the MAX7324, and then
issues a STOP condition. In this case, the MAX7324
resamples the port outputs during each acknowledge
and transmits the new data each time.
D6
I2
D2
S = START CONDITION
P = STOP CONDITION
P5
I1
D5
D1
I0
P4
D0
t
D4
PS
DATA 1
A
P3
PORT SNAPSHOT TAKEN
D3
F7
D7 D6
and Eight Inputs
P2
D2
F6
A = ACKNOWLEDGE
P1
F5
D5
D1
F4
D4
P0
D0
F3
D3
PORT SNAPSHOT
A
F2
D2
F1
D1 D0
ACKNOWLEDGE
FROM MASTER
P
F0
A
ACKNOWLEDGE
FROM MASTER
FLAG
t
IP
P
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