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Register Descriptions

Power-On Reset

PCA9536

WITH CONFIGURATION REGISTERS

SCPS125C – APRIL 2006 – REVISED NOVEMBER 2006

The Input Port register (register 0) reflects the incoming logic levels of the pins, regardless of whether the pin is

defined as an input or an output by the Configuration register. It only acts on read operation. Writes to these

registers have no effect. The default value, X, is determined by the externally applied logic level.

Input Port register will be accessed next.

Register 0 (Input Port Register)

I7

I6

I5

I4

BIT

I3

I2

I1

I0

Not Used

DEFAULT

1

1

1

1

X

X

X

X

The Output Port register (register 1) shows the outgoing logic levels of the pins defined as outputs by the

Configuration register. Bit values in this register have no effect on pins defined as inputs. In turn, reads from this

register reflect the value that is in the flip-flop controlling the output selection, not the actual pin value.

Register 1 (Output Port Register)

O7

O6

O5

O4

BIT

O3

O2

O1

O0

Not Used

DEFAULT

1

1

1

1

1

1

1

1

The Polarity Inversion register (register 2) allows polarity inversion of pins defined as inputs by the Configuration

register. If a bit in this register is set (written with 1), the corresponding port pin's polarity is inverted. If a bit in

this register is cleared (written with a 0), the corresponding port pin's original polarity is retained.

Register 2 (Polarity Inversion Register)

N7

N6

N5

N4

BIT

N3

N2

N1

N0

Not Used

DEFAULT

0

0

0

0

0

0

0

0

The Configuration register (register 3) configures the directions of the I/O pins. If a bit in this register is set to 1,

the corresponding port pin is enabled as an input with high-impedance output driver. If a bit in this register is

cleared to 0, the corresponding port pin is enabled as an output.

Register 3 (Configuration Register)

C7

C6

C5

C4

BIT

C3

C2

C1

C0

Not Used

DEFAULT

1

1

1

1

1

1

1

1

then back up to the operating voltage for a power-reset cycle.

7

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