PCA9537_5

© NXP B.V. 2009. All rights reserved.

Product data sheet

Rev. 05 — 7 May 2009

5 of 24

NXP Semiconductors

PCA9537

6.2.3 Register 1 - Output Port register

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.

6.2.4 Register 2 - Polarity Inversion register

This register allows the user to invert the polarity of the Input Port register data. If a bit in

this register is set (written with 1), the corresponding Input Port data is inverted. If a bit in

this register is cleared (written with a 0), the Input Port data polarity is retained.

Table 5.

Register 1 - Output Port register bit description

Legend: * default value.

Bit

Symbol

Access

Value

Description

7

O7

R

1*

not used

6O6

R

1*

5O5

R

1*

4O4

R

1*

3

O3

R

1*

reflects outgoing logic levels of pins defined as outputs

by Register 3

2O2

R

1*

1O1

R

1*

0O0

R

1*

Table 6.

Register 2 - Polarity Inversion register bit description

Legend: * default value.

Bit

Symbol

Access

Value

Description

7

N7

R/W

0*

not used

6

N6

R/W

0*

5

N5

R/W

0*

4

N4

R/W

0*

3

N3

R/W

0*

inverts polarity of Input Port register data

0 = Input Port register data retained (default value)

1 = Input Port register data inverted

2

N2

R/W

0*

1

N1

R/W

0*

0

N0

R/W

0*