Datasheet

RESET Input
Interrupt ( INT) Output
Bus Transactions
Writes
1 2
SCL
3 4 5 6 7 8
SDA
A A A
Data 0
R/W
t
pv
9
00 0 0 0 0 0 1
0.7 0.0
Data 11.7
1.0
A
S 1 1 1 0 1 A1 A0 0
t
pv
P
Slave Address
Command Byte Data to Port 0 Data to Port 1
Start Condition
Acknowledge
From Slave
Write to Port
Data Out from Port 1
Data Out from Port 0
Data Valid
Acknowledge
From Slave
Acknowledge
From Slave
TCA9539
SCPS202A – AUGUST 2009 – REVISED SEPTEMBER 2009 ........................................................................................................................................... www.ti.com
A reset can be accomplished by holding the RESET pin low for a minimum of t
W
. The TCA9539 registers and
I
2
C/SMBus state machine are held in their default states until RESET is once again high. This input requires a
pullup resistor to V
CC
, if no active connection is used.
An interrupt is generated by any rising or falling edge of the port inputs in the input mode. After time, t
iv
, the
signal INT is valid. Resetting the interrupt circuit is achieved when data on the port is changed to the original
setting or data is read from the port that generated the interrupt. Resetting occurs in the read mode at the
acknowledge (ACK) bit or not acknowledge (NACK) bit after the falling edge of the SCL signal. Interrupts that
occur during the ACK or NACK clock pulse can be lost (or be very short) due to the resetting of the interrupt
during this pulse. Each change of the I/Os after resetting is detected and is transmitted as INT.
Reading from or writing to another device does not affect the interrupt circuit, and a pin configured as an output
cannot cause an interrupt. 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. Because each 8-bit port is read
independently, the interrupt caused by port 0 is not cleared by a read of port 1, or vice versa.
INT has an open-drain structure and requires a pullup resistor to V
CC
.
Data is exchanged between the master and TCA9539 through write and read commands.
Data is transmitted to the TCA9539 by sending the device address and setting the least-significant bit to a logic 0
(see Figure 4 for device address). The command byte is sent after the address and determines which register
receives the data that follows the command byte.
The eight registers within the TCA9539 are configured to operate as four register pairs. The four pairs are Input
Ports, Output Ports, Polarity Inversion ports, and Configuration ports. After sending data to one register, the next
data byte is sent to the other register in the pair (see Figure 6 and Figure 7 ). For example, if the first byte is sent
to Output Port 1 (register 3), the next byte is stored in Output Port 0 (register 2).
There is no limitation on the number of data bytes sent in one write transmission. In this way, each 8-bit register
may be updated independently of the other registers.
Figure 6. Write to Output Port Registers
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