PCA9543 Philips Semiconductors, PCA9543 Datasheet - Page 4

• Manufacturer Part Number: PCA9543
• Description: 2-channel I2C switch with interrupt logic and reset
• Manufacturer: Philips Semiconductors

Philips Semiconductors
DEVICE ADDRESS
Following a START condition the bus master must output the
address of the slave it is accessing. The address of the PCA9543 is
shown in Figure 3. To conserve power, no internal pull-up resistors
are incorporated on the hardware selectable address pins and they
must be pulled HIGH or LOW.
The last bit of the slave address defines the operation to be
performed. When set to logic 1, a read is selected while a logic 0
selects a write operation.
CONTROL REGISTER
Following the successful acknowledgement of the slave address,
the bus master will send a byte to the PCA9543, which will be stored
in the control register. If multiple bytes are received by the
PCA9543, it will save the last byte received. This register can be
written and read via the I
CONTROL REGISTER DEFINITION
One or several SCx/SDx downstream pair, or channel, is selected
by the contents of the control register. This register is written after
the PCA9543 has been addressed. The 2 LSBs of the control byte
are used to determine which channel is to be selected. When a
channel is selected, the channel will become active after a stop
condition has been placed on the I
SCx/SDx lines will be in a HIGH state when the channel is made
active, so that no false conditions are generated at the time of
connection.
Table 1. Control Register; Write — Channel Selection/
Read — Channel Status
NOTE: Channel 0 and 1 can be enabled at the same time. Care
should be taken not to exceed the maximum bus capacitance.
2004 Oct 01
D7
X
X
X
X
0
2-channel I
7
7
D6
X
X
X
X
0
6
INTERRUPT BITS
6
INT1
1
(READ ONLY)
X
X
X
X
0
INT1 INT0
5
1
Figure 4. Control Register
FIXED
INT0
Figure 3. Slave address
2
4
X
X
X
X
0
1
C switch with interrupt logic and reset
2
C-bus.
0
3
X
D3
CHANNEL SELECTION BITS
X
X
X
X
0
0
HARDWARE SELECTABLE
2
X
(READ/WRITE)
2
A1 A0
D2
C-bus. This ensures that all
X
X
X
X
0
1
B1
B1
R/W
0
B0
X
X
0
1
0
B0
X
X
0
0
1
CHANNEL 0
CHANNEL 1
INT0
INT1
Channel 0
disabled
Channel 0
enabled
Channel 1
disabled
Channel 1
enabled
No channel
selected;
power-up/
reset default
state
COMMAND
SW01025
SW00893
4
INTERRUPT HANDLING
The PCA9543 provides 2 interrupt inputs, one for each channel, and
one open drain interrupt output. When an interrupt is generated by any
device, it will be detected by the PCA9543 and the interrupt output
will be driven LOW. The channel need not be active for detection of
the interrupt. A bit is also set in the Control Register.
Bits 4 – 5 of the Control Register correspond to the INT0 and INT1
inputs of the PCA9543, respectively. Therefore, if an interrupt is
generated by any device connected to channel 1, the state of the
interrupt inputs is loaded into the control register when a read is
accomplished. Likewise, an interrupt on any device connected to
channel 0 would cause bit 4 of the control register to be set on the
read. The master can then address the PCA9543 and read the
contents of the Control Register to determine which channel
contains the device generating the interrupt. The master can then
reconfigure the PCA9543 to select this channel, and locate the
device generating the interrupt and clear it.
It should be noted that more than one device can be providing an
interrupt on a channel, so it is up to the master to ensure that all
devices on a channel are interrogated for an interrupt.
The interrupt inputs may be used as general purpose inputs if the
interrupt feature is not required.
If unused, interrupt input(s) must be connected to V
pull-up resistor.
Table 2. Control Register Read — Interrupt
NOTE: The two interrupts can be active at the same time.
RESET INPUT
The RESET input is an active-LOW signal which may be used to
recover from a bus fault condition. By asserting this signal LOW for
a minimum of t
machine and will deselect all channels. The RESET input must be
connected to V
POWER-ON RESET
When power is applied to V
the PCA9543 in a reset state until V
point, the reset condition is released and the PCA9543 registers and
I
causing all the channels to be deselected.
2
C state machine are initialized to their default states, all zeroes
7
X
X
X
X
X
X
X
X
6
INT1
WL
DD
X
X
0
1
, the PCA9543 will reset its registers and I
through a pull-up resistor.
INT0
X
X
0
1
DD
3
X
X
X
X
, an internal Power-On Reset holds
DD
X
X
X
X
2
has reached V
B1
X
X
X
X
PCA9543
B0
X
X
X
X
Product data sheet
DD
POR
No interrupt
on channel 0
Interrupt on
channel 0
No interrupt
on channel 1
Interrupt on
channel 1
through a
COMMAND
. At this
2
C state