PCA9537 查看數據表（PDF） - Philips Electronics

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PCA9537

4-bit I2C and SMBus low power I/O port with interrupt and reset

Philips Electronics 

Philips Semiconductors

4-bit I2C and SMBus low power I/O port

with interrupt and reset

Product data sheet

PCA9537

REGISTERS

Command Byte

Command

Protocol

Function

0

Read byte

Input port register

1

Read/write byte Output port register

2

Read/write byte Polarity inversion register

3

Read/write byte Configuration register

The command byte is the first byte to follow the address byte during

a write transmission. It is used as a pointer to determine which of the

following registers will be written or read.

Register 0 – Input Port Register

bit

I7

I6 I5

I4 I3

I2 I1

I0

not used

default 1

1

1

1

X

X

X

X

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 value ‘X’ is determined by the externally applied logic

level.

Register 1 – Output Port Register

bit O7 O6 O5 O4 O3 O2 O1 O0

not used

default 1

1

1

1

1

1

1

1

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.

Register 2 – Polarity Inversion Register

bit N7 N6 N5 N4 N3 N2 N1 N0

not used

default 0

0

0

0

0

0

0

0

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.

Register 3 – Configuration Register

bit C7 C6 C5 C4 C3 C2 C1 C0

not used

default 1

1

1

1

1

1

1

1

This register configures the directions of the I/O pins. If a bit in this

register is set, the corresponding port pin is enabled as an input with

high impedance output driver. If a bit in this register is cleared, the

corresponding port pin is enabled as an output. At reset, the I/Os are

configured as inputs.

Power-on Reset

When power is applied to VDD, an internal power-on reset holds the

PCA9537 in a reset condition until VDD has reached VPOR. At that

point, the reset condition is released and the PCA9537 registers and

state machine will initialize to their default states. Thereafter, VDD

must lowered below 0.2 V to reset the device.

For a power reset cycle, VDD must be lowered below 0.2 V and then

restored to the operating voltage.

RESET Input

A reset can be accomplished by holding the RESET pin LOW for a

minimum of tW. The PCA9537 registers and SMBus/I2C state

machine will be held in their default state until the RESET input is

once again HIGH. This input requires a pull-up resistor to VDD if no

active connection is used.

Interrupt Output

The open-drain interrupt output is activated when one of the port

pins change state and the pin is configured as an input. The

interrupt is deactivated when the input returns to its previous state or

the input port register is read.

Note that changing an I/O from an output to an input may cause a

false interrupt to occur if the state of the pin does not match the

contents of the input port register.

2004 Nov 29

4

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