@terrypacker
NOW I understand! The offset is determined using predefined starting addresses by function from the MODBUS specification! Your explanation and that website you pointed me to was far more informative than watching a bunch of YouTube videos! Thank you so much for you help!

For those who find this thread later in life, here is what works (as of CLICK firmware 3.21):

  public static void main( String[] args ) throws Exception
  {
    /* Define Connection */
    IpParameters ipParameters = new IpParameters();
    ipParameters.setHost( "10.3.17.132" );
    ipParameters.setPort( 502 );

    /* Make the connection */
    ModbusMaster master = new ModbusFactory().createTcpMaster( ipParameters, false );
    master.init();

    /* Test connectivity */
    System.out.println( "testSlaveNode 1: " + master.testSlaveNode( 1 ) );

    /* Define the location points and type */
    BaseLocator< Boolean > clickX001 = BaseLocator.inputStatus( 1, 0 ); // Click X001: input BIT on CPU
    BaseLocator< Boolean > clickY001 = BaseLocator.coilStatus( 1, 0 ); // Click Y001: output COIL on CPU
    BaseLocator< Boolean > clickY002 = BaseLocator.coilStatus( 1, 1 ); // Click Y002: output COIL on CPU
    BaseLocator< Number > clickDS1 = BaseLocator.holdingRegister( 1, 0, DataType.TWO_BYTE_INT_SIGNED ); // Click DS1: Data Register Single Word

    /* Set/Write a value to a point */
    master.setValue( clickDS1, 1 );

    /* Get/Read the current value of each point */
    System.out.println( "clickX001  : " + master.getValue( clickX001 ) );
    System.out.println( "clickY001  : " + master.getValue( clickY001 ) );
    System.out.println( "clickY002  : " + master.getValue( clickY002 ) );
    System.out.println( "clickDS1   : " + master.getValue( clickDS1 ) );
  }

PLC Program for testing:

I'm new to modbus4j and MODBUS. I have been tasked with reading data from a CLICK (Koyo) PLC. According to the CLICK Programming Software, the MODBUS 984 Address for the BIT I am trying to read (Address X001) is 100001 with function code 02:

However, the 100001 address doesn't seem to work with modbus4j. I suspect the value used for OFFSET is not correct. Here is what I have tried:

  public static void main( String[] args ) throws Exception
  {
    IpParameters ipParameters = new IpParameters();
    ipParameters.setHost( "10.3.17.132" );
    ipParameters.setPort( 502 );

    ModbusMaster master = new ModbusFactory().createTcpMaster( ipParameters, false );
    master.init();

    // Define the location (X001).
    BaseLocator< Boolean > inputStatus = BaseLocator.inputStatus( 1, 100001 );
    BaseLocator< Boolean > inputRegisterBit = BaseLocator.inputRegisterBit( 1, 100001, 1 );

    // Read the value
    System.out.println( master.getValue( inputStatus ) );
    System.out.println( master.getValue( inputRegisterBit ) );
  }

This...

BaseLocator< Boolean > inputStatus = BaseLocator.inputStatus( 1, 100001 );

...always returns FALSE. Although the BIT is TRUE/ON (software and indicator light confirm this) the code is always reporting FALSE.

This...

BaseLocator< Boolean > inputRegisterBit = BaseLocator.inputRegisterBit( 1, 100001, 1 );

... returns an exception:
com.serotonin.modbus4j.exception.ModbusTransportException: Invalid offset: 100001

Would someone please help me understand how to convert the MODBUS 984 Address to a modbus4j offset? Or am I going about this completely wrong?