MAX7319 Maxim, MAX7319 Datasheet - Page 10

• Manufacturer Part Number: MAX7319
• Description: The MAX7319 2-wire serial-interfaced peripheral features eight input ports with selectable internal pullups, overvoltage protection to +6V, and transition detection with interrupt output
• Manufacturer: Maxim

The MAX7319 has a 7-bit slave address (Figure 5). The
8th bit following the 7-bit slave address is the R/W bit. It
is low for a write command, and high for a read com-
mand.
The 1st (A6), 2nd (A5), and 3rd (A4) bits of the MAX7319
slave address are always 1, 1, and 0. Connect AD2 and
AD0 to GND, V+
bits A3, A2, A1, and A0. The MAX7319 has 16 possible
slave addresses (Table 3), allowing up to 16 MAX7319
devices on an I
I
follows (Table 2).
A single-byte read from the MAX7319 returns the sta-
tus of the eight input ports, and clears both the internal
transition flags and the INT output (Figure 7).
I
Maskable Transition Detection
Figure 5. Slave Address
Figure 6. Reading from the MAX7319 (1 Data Byte)
10
2
C-interface access to the MAX7319 is summarized as
2
.
SDA
SCL
C Port Expander with Eight Inputs and
______________________________________________________________________________________
t
IV
MSB
1
PORT INPUT
INT OUTPUT
2
S
C bus
,
SCL
SDA, or SCL to select slave address
1
1
1
Accessing the MAX7319
0
MAX7319 SLAVE ADDRESS
0
Slave Address
A3
R/W
1
A
A2
t
IR
t
PH
A 2-byte read returns the status of the eight input ports
(as for a single-byte read), followed by the transition
flags. The internal transition flags and the INT output
are cleared when the MAX7319 acknowledges the
slave address byte, but the previous transition flag data
is sent as the second byte (Figure 8).
A multibyte read (more than 2 bytes before the I
STOP bit) repeatedly returns the input port data, alter-
nating with the transition flags. As the input data is
resampled for each transmission, and the transition
flags are reset each time, a multibyte read continuously
returns the current data and identifies any changing
input ports.
If a port input data change occurs during the read
sequence, INT is reasserted after the I
MAX7319 does not generate another interrupt during a
single-byte or multibyte read.
PORT SNAPSHOT
I7
D7
I6
INT REMAINS HIGH UNTIL STOP CONDITION
S = START CONDITION
P = STOP CONDITION
D6
A1
I5
D5
PORT INPUTS
I4
D4
I3
LSB
D3
A0
I2
D2
SHADED = SLAVE TRANSMISSION
N = NOT ACKNOWLEDGE
PORT SNAPSHOT
I1
D1
R/W
I0
D0
t
PSU
2
N
C STOP bit. The
ACK
P
t
IP
2
C