MAX7325 Maxim, MAX7325 Datasheet - Page 12

• Manufacturer Part Number: MAX7325
• Description: The MAX7325 2-wire serial-interfaced peripheral features 16 I/O ports
• Manufacturer: Maxim

I
and 8 Open-Drain I/Os
If a port input data change occurs during the read
sequence, then INT is reasserted during the I
bit. The MAX7325 does not generate another interrupt
during 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 two-byte read).
A multibyte read from the push-pull ports of the
MAX7325 repeatedly returns the status of the eight out-
put ports, read back as inputs.
A single-byte write to either port groups of the
MAX7325 sets the logic state of all eight ports.
A multibyte write to either port group of the MAX7325
repeatedly sets the logic state of all eight ports.
Figure 6. Reading Open-Drain Ports of the MAX7325 (1 Data Byte)
12
2
C Port Expander with 8 Push-Pull
______________________________________________________________________________________
t
IV
PORT
INT OUTPUT
S
SCL
1
1
0
MAX7325 SLAVE ADDRESS
2
FROM MAX7325
ACKNOWLEDGE
2
C STOP
R/W
C slave
1
2
C
A
t
t
IR
PH
PORT SNAPSHOT
P7
A read from the open-drain I/O ports of the MAX7325
starts with the master transmitting the port group’s
slave address with the R/W bit set to high. The
MAX7325 acknowledges the slave address, and sam-
ples the ports during the acknowledge bit. INT
deasserts during the slave address acknowledge.
Typically, the master reads 1 or 2 bytes from the
MAX7325, 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 open-drain
ports of the MAX7325 and subsequently issues a STOP
condition (Figure 6), the MAX7325 transmits the current
port data, clears the change flags, and resets the tran-
sition detection. INT deasserts during the slave
D7
P6
INT REMAINS HIGH UNTIL STOP CONDITION
D6
P5
S = START CONDITION
P = STOP CONDITION
D5
P4
PORT I/O
D4
P3
D3
P2
D2
PORT SNAPSHOT
P1
SHADED = SLAVE TRANSMISSION
N = NOT ACKNOWLEDGE
D1
P0
Reading the MAX7325
D0
t
PSU
ACKNOWLEDGE
FROM MASTER
N
P
t
IP