CAT9534
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10
Interrupt Output
CAT9534’s interrupt otuput is an active LOW open−drain
output that is activated when any port pin configured as an
input changes state. The interrupt output is reset when the
input returns to its previous state or the Input Port Register
is read.
Note that changing an I/O from an output to an input may
cause a false interrupt to occur if the state of the pin does not
match the contents of the Input Port register.
Power−On Reset Operation
When the power supply is applied to V
CC
pin, an internal
power−on reset pulse holds the CAT9534 in a reset state until
V
CC
reaches V
POR
level. At this point, the reset condition is
released and the internal state machine and the CAT9534’s
registers are initialized to their default state.
12345678 9
SCL
SDA
READ FROM
PORT
DATA INTO
PORT
S0100A2 A01
A
A1
A
DATA 4
NA P
no acknowledge
from master
acknowledge
from master
acknowledge
from slave
slave address
data from port
start condition
stop
condition
DATA 2
DATA 3 DATA 4
DATA 1
data from port
DATA 1
DATA
S0100A2 A00
A
A1
0 1 0 0 A2 A1 A0 A
DATA
A
acknowledge from master
acknowledge from slave
slave address
slave address data from register
COMMAND BYTE
AS
1
acknowledge from slave
acknowledge from slave
At this moment master−transmitter becomes
master−receiver and slave−receiver
becomes slave−transmitter
NA
no acknowledge
from master
data from register
P
last byte
first byte
Figure 11. Read from Register
Figure 12. Read Input Port Register
t
IR
t
IV
INT
t
PH
R/W
t
PS
R/W
R/W
