SCPS128D July   2006  – March 2021 PCA9554


  1. Features
  2. Description
  3. Revision History
  4. Description (Continued)
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 I2C Interface Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Functional Block Diagram
    2. 8.2 Device Functional Modes
      1. 8.2.1 Power-On Reset
      2. 8.2.2 I/O Port
      3. 8.2.3 Interrupt Output ( INT)
        1. Interrupt Errata
          1.        23
          2. 24
          3. 25
    3. 8.3 Programming
      1. 8.3.1 I2C Interface
      2. 8.3.2 Register Map
        1. Device Address
        2. Control Register And Command Byte
        3. Register Descriptions
        4. Bus Transactions
          1. Writes
          2. Reads
  9. Application Information Disclaimer
    1. 9.1 Application Information
      1. 9.1.1 Typical Application
        1. Design Requirements
          1. Minimizing ICC When I/Os Control Leds
  10. 10Power Supply Recommendations
    1. 10.1 Power-On Reset Requirements
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Register Descriptions

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.

Before a read operation, a write transmission is sent with the command byte to indicate to the I2C device that the Input Port register will be accessed next.

Table 8-4 Register 0 (Input Port Register) Table

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.

Table 8-5 Register 1 (Output Port Register) Table

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

Table 8-6 Register 2 (Polarity Inversion Register) Table

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.

Table 8-7 Register 3 (Configuration Register) Table