MAX7324 Maxim, MAX7324 Datasheet - Page 9

• 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

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 2 bytes of input port data followed by 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 MAX7324 includes an 8-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 routine. Instead, if a data change occurs that
would normally cause the INT output to be set, the INT
assertion is delayed until the STOP condition. INT is not
Table 3. MAX7324 Address Map for Outputs O8–O15
I
PIN CONNECTION
GND
GND
GND
GND
2
AD2
SDA
SDA
SDA
SDA
SCL
SCL
SCL
SCL
V+
V+
V+
V+
C Port Expander with Eight Push-Pull Outputs
GND
GND
GND
GND
AD0
SCL
SDA
SCL
SDA
SCL
SDA
SCL
SDA
V+
V+
V+
V+
_______________________________________________________________________________________
A6
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
A5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
DEVICE ADDRESS
A4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
A3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
A2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
A1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
A0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
O15
reasserted upon a STOP condition if the changed input
data is read before the STOP occurs. The INT logic
ensures 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 transition
flag and an interrupt mask bit for each input port. The
eight transition flags can be read through the serial
interface, and the 8-bit interrupt mask is set through the
serial interface.
Each port’s transition 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 MAX7324 periodically to monitor less-
important inputs. The transition flags indicate whether a
permanent or transient change has occurred on any
input since the MAX7324 was last accessed.
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
O14
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
OUTPUTS POWER-UP DEFAULT
O13
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
and Eight Inputs
Transition-Detection Masks
O12
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
O11
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
O10
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
O9
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
O8
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
9