MAX7328 Maxim, MAX7328 Datasheet - Page 6

• Manufacturer Part Number: MAX7328
• Description: The MAX7328/MAX7329 are 2-wire serial-interfaced peripherals with eight I/O ports
• Manufacturer: Maxim

Interrupts that occur during the acknowledge clock
pulse may be lost (or very short) due to the resetting of
the interrupt during this pulse. Each change of the I/Os
after resetting is detected and, after the next rising
clock edge, is transmitted as INT.
On power-up, the power-up default states of the eight
I/O ports are high, and therefore, can be used as inputs
or outputs. The interrupt output INT is reset, and INT
goes high (high impedance if an external pullup resistor
is not fitted).
I
Figure 2. Repeated Write Operation Showing Transient Pullup Current
6
Figure 3. 2-Wire Serial-Interface Timing Details
2
_______________________________________________________________________________________
C Port Expanders with Eight I/O Ports
SDA
SCL
OUTPUT CURRENT
t
HD, STA
MAX7328/MAX7329 Initial Power-Up
START CONDITION
P3 PULLUP
VOLTAGE
OUTPUT
SDA
SCL
P3
START CONDITION
S
t
LOW
1
2
t
SLAVE ADDRESS
R
3
t
SU, DAT
t
HIGH
4
t
F
5
6
t
HD, DAT
7
R/W ACKNOWLEDGE
0
8
A
FROM SLAVE
t
VD, DAT
t
SU, STA
REPEATED START CONDITION
DATA TO PORT
The MAX7328/MAX7329 operate as slave devices that
send and receive data through an I
2-wire interface. The interface uses a serial-data line
(SDA) and a serial-clock line (SCL) to achieve bidirec-
tional communication between master(s) and slave(s).
A master initiates all data transfers to and from the
MAX7328 or MAX7329, and generates the SCL clock
that synchronizes the data transfer (Figure 3).
The MAX7328 or MAX7329 SDA line operates as both
an input and an open-drain output. A pullup resistor,
P3
1
t
HD, STA
I
OHt
A
DATA TO PORT
t
SU, STO
P3
Serial Interface
0
CONDITION
Serial Addressing
STOP
t
BUF
2
C-compatible,
CONDITION
A
I
START
OH
P