MAX7327 Maxim, MAX7327 Datasheet - Page 9

• Manufacturer Part Number: MAX7327
• Description: The MAX7327, a 2-wire serial-interfaced peripheral, features 12 push-pull outputs and four configurable open-drain I/O ports with selectable internal pullups and transition detection
• Manufacturer: Maxim

I/O port inputs switch at CMOS logic levels as deter-
mined by the expander’s supply voltage, and are over-
voltage tolerant to +6V, independent of the expander’s
supply voltage.
All I/O ports configured as inputs are monitored for
changes since the expander was last accessed
through the serial interface. The state of the ports is
stored in an internal “snapshot” register for transition
monitoring. The snapshot is continuously compared
with the actual input conditions, and if a change is
detected for any port input, INT is asserted to signal a
state change. The input ports are sampled (internally
latched into the snapshot register) and the old transi-
tion flags cleared during the I
MAX7327 read and write access. The previous port
transition flags are read through the serial interface as
the second byte of a 2-byte read sequence.
Table 3. MAX7327 Address Map for Outputs O8–O15
C O NN EC TIO N
GND
GND
GND
GND
AD2
SDA
SDA
SDA
SDA
SCL
SCL
SCL
SCL
V+
V+
V+
V+
PIN
GND
GND
GND
GND
AD0
SDA
SDA
SDA
SDA
SCL
SCL
SCL
SCL
V+
V+
V+
V+
I/O Port Input Transition Detection
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
I
DEVICE ADDRESS
A4
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
C acknowledge of every
C Port Expander with 12 Push-Pull
A3
I/O Port Inputs
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Outputs and 4 Open-Drain I/Os
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
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 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
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.
O15
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
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
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