MAX7324 Maxim, MAX7324 Datasheet - Page 12

• 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

If a port input data change occurs during the read
sequence, INT is reasserted during the I
The MAX7324 does not generate another interrupt dur-
ing a single-byte or multibyte read.
Input-port data is sampled during the preceding I
acknowledge bit (the acknowledge bit for the I
address in the case of a single-byte or 2-byte read).
A multibyte read (more than 2 bytes before the I
STOP bit) from the output ports of the MAX7324 repeat-
edly returns the status of the eight output ports, read
back as inputs.
A single-byte write to the input ports of the MAX7324
sets the interrupt mask register and clears both the
internal transition flags and INT output.
A single-byte write to the output ports of the MAX7324
sets the logic state of all eight ports.
A multibyte write to the input ports of the MAX7324
sets the interrupt mask register repeatedly.
A multibyte write to the output ports of the MAX7324
repeatedly sets the logic state of all eight ports.
I
and Eight Inputs
Figure 6. Reading Input Ports of the MAX7324 (1 Data Byte)
12
2
C Port Expander with Eight Push-Pull Outputs
______________________________________________________________________________________
t
IV
PORTS
INT OUTPUT
SCL
S
MAX7324 SLAVE ADDRESS
2
C STOP bit.
2
C slave
FROM MAX7324
ACKNOWLEDGE
R/W
2
2
C
C
1
A
A read from the input ports of the MAX7324 starts with
the master transmitting the input ports’ slave address
with the R/W bit set to high. The MAX7324 acknowl-
edges the slave address and samples the ports during
the acknowledge bit. INT deasserts during the slave
address acknowledge.
Typically, the master reads 1 or 2 bytes from the
MAX7324 with each byte being acknowledged by the
master upon reception with the exception of the last
byte.
When the master reads one byte from the open-drain
ports of the MAX7324 and subsequently issues a STOP
condition (Figure 6), the MAX7324 transmits the current
port data, clears the transition flags, and resets the
transition detection. INT deasserts during the slave
acknowledge. The new snapshot data is the current
port data transmitted to the master, and therefore, port
changes occuring during the transmission are detect-
ed. INT remains high until the STOP condition.
t
t
IR
PH
PORT SNAPSHOT
I7
D7
I6
INT REMAINS HIGH UNTIL STOP CONDITION
D6
I5
D5
S = START CONDITION
P = STOP CONDITION
I4
D4
I3
D3
I2
PORT SNAPSHOT
D2
Reading from the MAX7324
I1
D1
A = ACKNOWLEDGE
I0
D0
t
PS
ACKNOWLEDGE
FROM MASTER
A
P
t
IP