class    TUart1 : public TCustomUart
{
    public:
        TUart1(uint32_t baudrate) {hw_init(baudrate);}
    protected:
        ...
        virtual void hw_init(uint32_t baudrate);
        virtual void write_tx_reg(char ch) { TXBUF0 = ch; }
        static interrupt(UART0RX_VECTOR) usart0_rx(void);
        static interrupt(UART0TX_VECTOR) usart0_tx(void);
};

...

interrupt(UART0TX_VECTOR) TUart1::usart0_tx(void)
{
    OS::TISRW ISR;
    char ch;
    if (Uart1.TxChannel.get_count())
    {
        Uart1.TxChannel.pop(ch);
        TXBUF0 = ch;
    }
    else
    {
        Uart1.tx_active = false;
    }
}

void TUart1::hw_init(uint32_t baudrate)
{
    typedef void (* Handler)(void);
    volatile Handler ptr;
    ...
    ptr = &usart0_rx;
    ptr = &usart0_tx;
}