PCA9548ABS データシートの表示（PDF） - Philips Electronics

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PCA9548ABS

8-channel I2C switch with reset

Philips Electronics 

Philips Semiconductors

PCA9548A

8-channel I2C switch with reset

7.2.1 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.

7.3 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 tWL, 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.

7.4 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.

9397 750 13297

Product data sheet

Rev. 01 — 15 April 2005

© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

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