PCA9554 查看數據表（PDF） - ON Semiconductor

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PCA9554

8-bit I2C and SMBus I/O Port with Interrupt

ON Semiconductor 

PCA9554

Power−On Reset Operation

When the power supply is applied to VCC pin, an internal

power−on reset pulse holds the PCA9554 in a reset state

until VCC reaches VPOR level. At this point, the reset

condition is released and the internal state machine and the

PCA9554’s registers are initialized to their default state.

slave address R/W

slave address

acknowledge from master

R/W

data from register

S 0 1 0 0 A2 A1 A0 0 A

acknowledge from slave

COMMAND BYTE A S 0 1 0 0 A2 A1 A0 1 A

acknowledge from slave

acknowledge from slave

DATA

A

first byte

At this moment master−transmitter becomes

master−receiver and slave−receiver

becomes slave−transmitter

no acknowledge

from master

data from register

DATA

last byte

NA P

Figure 11. Read from Register

SCL

123456 78 9

slave address

R/W

SDA S 0 1 0 0 A2 A1 A0 1 A

start condition

READ FROM

PORT

acknowledge

from slave

DATA INTO

PORT

DATA 1

tPH

data from port

DATA 1

A

acknowledge

from master

DATA 2

DATA 3

tPS

data from port

DATA 4

NA P

no acknowledge

from master

stop

condition

DATA 4

INT

tIV

tIR

Figure 12. Read Input Port Register

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