PCA9548A(2009) 查看數據表（PDF） - NXP Semiconductors.
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PCA9548A Datasheet PDF : 26 Pages
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NXP Semiconductors
PCA9548A
8-channel I2C-bus switch with reset
6.2.1 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 PCA9548A 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 I2C-bus. This ensures that all 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 4. Control register: Write—channel selection; Read—channel status
B7 B6 B5 B4 B3 B2 B1 B0 Command
0
channel 0 disabled
X
X
X
X
X
X
X
1
channel 0 enabled
0
channel 1 disabled
X
X
X
X
X
X
X
1
channel 1 enabled
0
channel 2 disabled
X
X
X
X
X
X
X
1
channel 2 enabled
0
channel 3 disabled
X
X
X
X
X
X
X
1
channel 3 enabled
0
channel 4 disabled
X
X
X
X
X
X
X
1
channel 4 enabled
0
channel 5 disabled
X
X
X
X
X
X
X
1
channel 5 enabled
0
channel 6 disabled
X
X
X
X
X
X
X
1
channel 6 enabled
0
channel 7 disabled
X
X
X
X
X
X
X
1
channel 7 enabled
Remark: Multiple channels can be enabled at the same time. Example: B7 = 0, B6 = 1,
B5 = 0, B4 = 0, B3 = 1, B2 = 1, B1 = 0, B0 = 0, means that channels 7, 5, 4, 1 and 0 are
disabled and channels 6, 3, and 2 are enabled. Care should be taken not to exceed the
maximum bus capacitance. Default condition is all zeroes.
6.3 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 tw(rst)L, the PCA9548A will reset
its register and I2C-bus state machine and will deselect all channels. The RESET input
must be connected to VDD through a pull-up resistor.
6.4 Power-on reset
When power is applied to VDD, an internal Power-On Reset (POR) holds the PCA9548A in
a reset condition until VDD has reached VPOR. At this point, the reset condition is released
and the PCA9548A register and I2C-bus state machine are initialized to their default
states (all zeroes) causing all the channels to be deselected. Thereafter, VDD must be
lowered below 0.2 V to reset the device.
PCA9548A_3
Product data sheet
Rev. 03 — 7 July 2009
© NXP B.V. 2009. All rights reserved.
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