MAX7319 Maxim, MAX7319 Datasheet - Page 11

• 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

Input port data is sampled during the preceding I
acknowledge bit (the acknowledge bit for the I
address in the case of a single-byte or 2-byte read).
A single-byte write to the MAX7319 sets the interrupt
mask register, and clears both the internal transition
flags and the INT output.
A multibyte write to the MAX7319 sets the interrupt
mask register repeatedly.
A read from the MAX7319 starts with the master trans-
mitting the MAX7319’s slave address with the R/W bit
set high. The MAX7319 acknowledges the slave
address and samples the input ports during acknowl-
edge bit. INT deasserts during the slave address
acknowledge.
Typically, the master reads 1 or 2 bytes from the
MAX7319, with each byte, except the last one, being
acknowledged by the master upon reception.
Figure 7. Reading from the MAX7319 (2 Data Bytes)
______________________________________________________________________________________
I
2
C Port Expander with Eight Inputs and
Reading from the MAX7319
Maskable Transition Detection
2
C slave
2
C
When the master reads 1 byte from the MAX7319 and
subsequently issues a STOP condition (Figure 6), the
MAX7319 transmits the current port data, clears the
transition flags, and resets the transition detection. INT
deasserts during the slave address acknowledge. The
new snapshot data is the current port data transmitted
to the master; therefore, port transitions ocurring during
the transmission are detected. INT remains high until
the STOP condition.
When the master reads 2 bytes from the MAX7319 and
subsequently issues a STOP condition (Figure 7), the
MAX7319 transmits the current port data, followed by
the transition flags. The transition flags are cleared, and
transition detection reset. INT deasserts during the
slave address acknowledge. The new snapshot data is
the current port data transmitted to the master; there-
fore, port transitions occurring during the transmission
are detected. INT remains high until the STOP condi-
tion. When the master reads more than 2 bytes, the
input port data alternates with the transition flag.
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
N = NOT ACKNOWLEDGE
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