pca9554ad NXP Semiconductors, pca9554ad Datasheet - Page 7

• Manufacturer Part Number: pca9554ad
• Description: 8-bit I2c And Smbus I/o Port With Interrupt
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA9554_9554A_7
Product data sheet
6.1.2 Register 0 - Input Port register
6.1.3 Register 1 - Output Port register
This register is a read-only port. It reflects the incoming logic levels of the pins, regardless
of whether the pin is defined as an input or an output by Register 3. Writes to this register
have no effect.
The default ‘X’ is determined by the externally applied logic level, normally ‘1’ when no
external signal externally applied because of the internal pull-up resistors.
Table 4.
This register reflects the outgoing logic levels of the pins defined as outputs by Register 3.
Bit values in this register have no effect on pins defined as inputs. Reads from this register
return the value that is in the flip-flop controlling the output selection, not the actual pin
value.
Table 5.
Legend: * default value.
Bit
7
6
5
4
3
2
1
0
Bit
7
6
5
4
3
2
1
0
Symbol
I7
I6
I5
I4
I3
I2
I1
I0
Symbol
O7
O6
O5
O4
O3
O2
O1
O0
Register 0 - Input Port register bit description
Register 1 - Output Port register bit description
Access
read only
read only
read only
read only
read only
read only
read only
read only
Access
R
R
R
R
R
R
R
R
Rev. 07 — 13 November 2006
Value
X
X
X
X
X
X
X
X
Value
1*
1*
1*
1*
1*
1*
1*
1*
8-bit I
Description
reflects outgoing logic levels of pins defined as
outputs by Register 3
Description
determined by externally applied logic level
2
PCA9554/PCA9554A
C-bus and SMBus I/O port with interrupt
© NXP B.V. 2006. All rights reserved.
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