MAX7321 Maxim, MAX7321 Datasheet - Page 6

• Manufacturer Part Number: MAX7321
• Description: The MAX7321 2-wire serial-interfaced peripheral features eight open-drain I/O ports with selectable internal pullups and transition detection
• Manufacturer: Maxim

case of a bus lockup, terminating any serial transaction
to or from the MAX7321.
Any port can be configured as a logic input by setting
the port output logic-high (logic-high for an open-drain
output is high impedance). When the MAX7321 is read
through the serial interface, the actual logic levels at
the ports are read back.
The open-drain ports offer latching transition detection
when used as inputs. All input ports are continuously
monitored for changes. An input change sets 1 of 8 flag
bits that identify changed input(s). All flags are cleared
upon a subsequent read or write transaction to the
MAX7321.
A latching interrupt output, INT, is programmed to flag
logic changes on ports used as inputs. Data changes
on any input port forces INT to a logic-low. Changing
the I/O port level through the serial interface does not
cause an interrupt. The interrupt output INT is deassert-
ed when the MAX7321 is next accessed through the
serial interface.
Internal pullup resistors to V+ are selected by the
address select inputs, AD0 and AD2. Pullups are
enabled on the input ports in groups of four (see
Use the slave address selection to ensure that I/O ports
used as inputs are logic-high on power-up. I/O ports with
I
Table 1. MAX7319–MAX7329 Family Comparison (continued)
6
16-PORT EXPANDERS
MAX7323
MAX7328
MAX7329
MAX7324
MAX7325
MAX7326
MAX7327
2
PART
_______________________________________________________________________________________
C Port Expander with 8 Open-Drain I/Os
ADDRESS
0100xxx
0111xxx
110xxxx
101xxxx
110xxxx
SLAVE
and
I
2
C
INPUTS
Up to 4
Up to 8
Up to 8
Up to 4
8
4
INTERRUPT
INPUT
MASK
Yes
Yes
—
—
—
—
OUTPUTS
Table 3).
Up to 4
Up to 8
Up to 8
Up to 4
OPEN-
DRAIN
—
—
OUTPUTS
PUSH-
PULL
internal pullups enabled default to a logic-high output
state. Ports with internal pullups disabled default to a
logic-low output state. Output port power-up logic
states are selected by the address select inputs AD0
and AD2. Ports default to logic-high or logic-low on
power-up in groups of four (see Table 3).
On power-up, the transition detection logic is reset, and
INT is deasserted. The transition flags are cleared to
indicate no data changes. The power-up default states
of the eight I/O ports are set according to the I
address selection inputs, AD0 and AD2 (Table 3). For
I/O ports used as inputs, ensure that the default
states are logic-high so that the I/O ports power up
in the high-impedance state. All I/O ports configured
with pullups enabled also have a logic-high power-
up state.
The MAX7321 contains an integral power-on reset
(POR) circuit that ensures all registers are reset to a
known state on power-up. When V+ rises above V
(1.6V max), the POR circuit releases the registers and
2-wire interface for normal operation. When V+ drops to
less than V
tents to the POR defaults (Table 3).
—
12
12
4
8
8
4 I/O, 4 output-only versions:
4 open-drain I/O ports with latching transition
detection interrupt and selectable pullups.
4 push-pull outputs with selectable power-up default
levels.
8 open-drain I/O ports with nonlatching transition
detection interrupt and pullups on all ports.
All ports power up as inputs (or logic-high outputs).
Any port can be used as an input by setting the
open-drain output to logic-high.
Software equivalent to a MAX7320 plus a MAX7319.
Software equivalent to a MAX7320 plus a MAX7321.
Software equivalent to a MAX7320 plus a MAX7322.
Software equivalent to a MAX7320 plus a MAX7323.
POR
, the MAX7321 resets all register con-
APPLICATION
Initial Power-Up
Power-On Reset
2
C slave
POR