MAX7322AEE+ Maxim Integrated Products, MAX7322AEE+ Datasheet - Page 9

• Manufacturer Part Number: MAX7322AEE+
• Description: IC I/O EXPANDER I2C 4B 16QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX7322AEE+

• Interface: I²C
• Number Of I /o: 4
• Interrupt Output: Yes
• Frequency - Clock: 400kHz
• Voltage - Supply: 1.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Includes: POR
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

“snapshot” register for transition monitoring. The snap-
shot is continuously compared with the actual input
conditions, and if a change is detected for any port
input, then an internal transition flag is set for that port,
and INT is asserted to signal a state change. The four
port inputs are sampled (internally latched into the
snapshot register) and the old transition flags cleared
during the I
and write access. The previous port transition flags are
read through the serial interface as the second byte of
a 2-byte read sequence.
A long read sequence (more than 2 bytes) can be used
to poll the expander continuously without the overhead
of resending the slave address. If more than 2 bytes
are read from the expander, the expander repeatedly
returns the input port data alternating with the transition
flags. The inputs are repeatedly resampled and the
transition flags repeatedly reset for each pair of bytes
read. All changes that occur during a long read
sequence are detected and reported.
The MAX7322 includes a 4-bit interrupt mask register
that selects which inputs generate an interrupt upon
change. Each input’s transition flag is set when its input
changes, independent of the interrupt mask register
settings. The interrupt mask register allows the proces-
sor to be interrupted for critical events, while the inputs
and the transition flags can be polled periodically to
detect less-critical events.
The INT output is not reasserted during a read sequence
to avoid recursive reentry into an interrupt service rou-
tine. Instead, if a data change occurs that would normal-
ly cause the INT output to be set, the INT assertion is
delayed until the STOP condition. INT is not reasserted
upon a STOP condition if the changed input data is
read before the STOP occurs. The INT logic ensures
Figure 1. 2-Wire Serial Interface Timing Details
SDA
SCL
t
HD,STA
START CONDITION
2
C acknowledge of every MAX7322 read
_______________________________________________________________________________________
t
LOW
t
R
t
SU,DAT
t
HIGH
t
F
4 Push-Pull Outputs and 4 Inputs
t
HD,DAT
t
REPEATED START CONDITION
SU,STA
I
that unnecessary interrupts are not asserted, yet data
changes are detected and reported no matter when the
change occurs.
The transition detection logic incorporates a change
flag and an interrupt mask bit for each of the four input
ports. The four change flags can be read through the
serial interface, and the 4-bit interrupt mask is set
through the serial interface.
Each port’s change flag is set when that port’s input
changes, and the change flag remains set even if the
input returns to its original state. The port’s interrupt
mask determines whether a change on that input port
generates an interrupt. Enable interrupts for high-priori-
ty inputs using the interrupt mask. The interrupt allows
the system to respond quickly to changes on these
inputs. Poll the MAX7322 periodically to monitor less-
important inputs. The change flags indicate whether a
permanent or transient change has occurred on any
input since the MAX7322 was last accessed.
Write one byte to the MAX7322 to set the output port
levels for the four push-pull outputs, and the interrupt
mask for the four inputs simultaneously.
The MAX7322 operates as a slave that sends and
receives data through an I
uses a serial-data line (SDA) and a serial-clock line (SCL)
to achieve bidirectional communication between mas-
ter(s) and slave(s). The master initiates all data transfers
to and from the MAX7322 and generates the SCL clock
that synchronizes the data transfer (Figure 1).
2
C Port Expander with
t
HD,STA
Transition Detection Masks
t
SU,STO
2
C interface. The interface
CONDITION
STOP
Serial Interface
Serial Addressing
Port Outputs
t
BUF
CONDITION
START
9