Управление модулем вывода из Visual Basic NET (NModbus)

Подскажите в чём проблема. Два модуля подключены через COM порт, у модуля ввода 32 адрес, у модуля вывода - 16. Данные регистра с модуля ввода читаю свободно, но записать данные в модуль вывода не могу... Ошибка "Необработанное исключение типа "Modbus.SlaveException" в NModbus4.dll". Полный текст ошибки:

Цитата:

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Выдано исключение типа "Modbus.SlaveException".
Function Code: 134
Exception Code: 1 - The function code received in the query is not an allowable action for the server (or slave). This may be because the function code is only applicable to newer devices, and was not implemented in the unit selected. It could also indicate that the server (or slave) is in the wrong state to process a request of this type, for example because it is unconfigured and is being asked to return register values.

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Листинг программы:

Код:

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Imports Modbus.Device
Imports System.IO

Public Class Form1

    Public master As ModbusSerialMaster
    Public serPort As Ports.SerialPort
    Public zzz As UShort()

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        serPort = New Ports.SerialPort("COM4", 115200, Ports.Parity.None, 8, Ports.StopBits.One)
        master = ModbusSerialMaster.CreateRtu(serPort)
        serPort.Open()
    End Sub

    Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
        zzz = master.ReadHoldingRegisters(32, 100, 1)
        Label1.Text = zzz(0)
    End Sub

    Private Sub Form1_FormClosed(sender As Object, e As FormClosedEventArgs) Handles MyBase.FormClosed
        serPort.Close()
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        master.WriteSingleRegister(16, 50, 1)
    End Sub
End Class

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Используйте функцию Write Multiple Registers.