&sh_chan->serial_tx_interrupt);
        cyg_drv_interrupt_attach(sh_chan->serial_tx_interrupt_handle);
        cyg_drv_interrupt_unmask(sh_chan->tx_int_num);
        sh_chan->tx_enabled = false;
    }
    if (chan->in_cbuf.len != 0) {
        // Receive interrupt
        cyg_drv_interrupt_create(sh_chan->rx_int_num,
                                 3,
                                 (cyg_addrword_t)chan, // Data item passed to interrupt handler
                                 sh_serial_rx_ISR,
                                 sh_serial_rx_DSR,
                                 &sh_chan->serial_rx_interrupt_handle,
                                 &sh_chan->serial_rx_interrupt);
        cyg_drv_interrupt_attach(sh_chan->serial_rx_interrupt_handle);
        // Receive error interrupt
        cyg_drv_interrupt_create(sh_chan->er_int_num,
                                 3,
                                 (cyg_addrword_t)chan, // Data item passed to interrupt handler
                                 sh_serial_er_ISR,
                                 sh_serial_er_DSR,
                                 &sh_chan->serial_er_interrupt_handle,
                                 &sh_chan->serial_er_interrupt);
        cyg_drv_interrupt_attach(sh_chan->serial_er_interrupt_handle);
        // This unmasks both interrupt sources.
        cyg_drv_interrupt_unmask(sh_chan->rx_int_num);
    }
    sh_serial_config_port(chan, &chan->config, true);
    return true;
}

// This routine is called when the device is "looked" up (i.e. attached)
static Cyg_ErrNo 
sh_serial_lookup(struct cyg_devtab_entry **tab, 
                  struct cyg_devtab_entry *sub_tab,
                  const char *name)
{
    serial_channel *chan = (serial_channel *)(*tab)->priv;

    // Really only required for interrupt driven devices
    (chan->callbacks->serial_init)(chan);
    return ENOERR;
}

// Send a character to the device output buffer.
// Return 'true' if character is sent to device
static bool
sh_serial_putc(serial_channel *chan, unsigned char c)
{
    cyg_uint8 _ssr;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSSR, _ssr);
    if (_ssr & CYGARC_REG_SCI_SCSSR_TDRE) {
// Transmit buffer is empty
        HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCTDR, c);
        // Clear empty flag.
        HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSSR, 
                        CYGARC_REG_SCI_SCSSR_CLEARMASK & ~CYGARC_REG_SCI_SCSSR_TDRE);
        return true;
    } else {
// No space
        return false;
    }
}

// Fetch a character from the device input buffer, waiting if necessary
static unsigned char 
sh_serial_getc(serial_channel *chan)
{
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;
    unsigned char c;
    cyg_uint8 _ssr;

    do {
        HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSSR, _ssr);
    } while ((_ssr & CYGARC_REG_SCI_SCSSR_RDRF) == 0);

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCRDR, c);

    // Clear buffer full flag.
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSSR, 
                    CYGARC_REG_SCI_SCSSR_CLEARMASK & ~CYGARC_REG_SCI_SCSSR_RDRF);

    return c;
}

// Set up the device characteristics; baud rate, etc.
static Cyg_ErrNo
sh_serial_set_config(serial_channel *chan, cyg_uint32 key,
                     const void *xbuf, cyg_uint32 *len)
{
    switch (key) {
    case CYG_IO_SET_CONFIG_SERIAL_INFO:
      {
        cyg_serial_info_t *config = (cyg_serial_info_t *)xbuf;
        if ( *len < sizeof(cyg_serial_info_t) ) {
            return -EINVAL;
        }
        *len = sizeof(cyg_serial_info_t);
        if ( true != sh_serial_config_port(chan, config, false) )
            return -EINVAL;
      }
      break;
    default:
        return -EINVAL;
    }
    return ENOERR;
}

// Enable the transmitter on the device
static void
sh_serial_start_xmit(serial_channel *chan)
{
    cyg_uint8 _scr;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;

    sh_chan->tx_enabled = true;

    // Mask the interrupts (all sources of the unit) while changing
    // the CR since a rx interrupt in the middle of this would result
    // in a bad CR state.
    cyg_drv_interrupt_mask(sh_chan->rx_int_num);

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    _scr |= CYGARC_REG_SCI_SCSCR_TIE;       // Enable xmit interrupt
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);

    cyg_drv_interrupt_unmask(sh_chan->rx_int_num);
}

// Disable the transmitter on the device
static void 
sh_serial_stop_xmit(serial_channel *chan)
{
    cyg_uint8 _scr;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;

    sh_chan->tx_enabled = false;

    // Mask the interrupts (all sources of the unit) while changing
    // the CR since a rx interrupt in the middle of this would result
    // in a bad CR state.
    cyg_drv_interrupt_mask(sh_chan->rx_int_num);

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    _scr &= ~CYGARC_REG_SCI_SCSCR_TIE;      // Disable xmit interrupt
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);

    cyg_drv_interrupt_unmask(sh_chan->rx_int_num);
}

// Serial I/O - low level tx interrupt handler (ISR)
static cyg_uint32 
sh_serial_tx_ISR(cyg_vector_t vector, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;
    cyg_uint8 _scr;

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    _scr &= ~CYGARC_REG_SCI_SCSCR_TIE;      // mask out tx interrupts
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);

    return CYG_ISR_CALL_DSR;  // Cause DSR to be run
}

// Serial I/O - high level tx interrupt handler (DSR)
static void       
sh_serial_tx_DSR(cyg_vector_t vector, cyg_ucount32 count, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;

    (chan->callbacks->xmt_char)(chan);

    if (sh_chan->tx_enabled) {
        cyg_uint8 _scr;

        HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
        _scr |= CYGARC_REG_SCI_SCSCR_TIE;       // unmask tx interrupts
        HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    }
}

// Serial I/O - low level RX interrupt handler (ISR)
static cyg_uint32 
sh_serial_rx_ISR(cyg_vector_t vector, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;
    cyg_uint8 _scr;

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    _scr &= ~CYGARC_REG_SCI_SCSCR_RIE;      // mask rx interrupts
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    return CYG_ISR_CALL_DSR;  // Cause DSR to be run
}

// Serial I/O - high level rx interrupt handler (DSR)
static void       
sh_serial_rx_DSR(cyg_vector_t vector, cyg_ucount32 count, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;
    cyg_uint8 _ssr, _scr;

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSSR, _ssr);
    if (_ssr & CYGARC_REG_SCI_SCSSR_RDRF) {
        cyg_uint8 _c;
        HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCRDR, _c);
        // Clear buffer full flag.
        HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSSR, 
                        CYGARC_REG_SCI_SCSSR_CLEARMASK & ~CYGARC_REG_SCI_SCSSR_RDRF);

        (chan->callbacks->rcv_char)(chan, _c);
    }

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    _scr |= CYGARC_REG_SCI_SCSCR_RIE;       // unmask rx interrupts
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
}

static volatile int sh_serial_error_orer = 0;
static volatile int sh_serial_error_fer = 0;
static volatile int sh_serial_error_per = 0;

// Serial I/O - low level error interrupt handler (ISR)
static cyg_uint32 
sh_serial_er_ISR(cyg_vector_t vector, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;
    cyg_uint8 _scr;

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    _scr &= ~CYGARC_REG_SCI_SCSCR_RIE;      // mask rx interrupts
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    return CYG_ISR_CALL_DSR;            // Cause DSR to be run
}

// Serial I/O - high level error interrupt handler (DSR)
static void       
sh_serial_er_DSR(cyg_vector_t vector, cyg_ucount32 count, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    sh_sci_info *sh_chan = (sh_sci_info *)chan->dev_priv;
    cyg_uint8 _ssr, _ssr2, _scr;

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSSR, _ssr);
    _ssr2 = CYGARC_REG_SCI_SCSSR_CLEARMASK;

    if (_ssr & CYGARC_REG_SCI_SCSSR_ORER) {
        _ssr2 &= ~CYGARC_REG_SCI_SCSSR_ORER;
        sh_serial_error_orer++;
    }
    if (_ssr & CYGARC_REG_SCI_SCSSR_FER) {
        _ssr2 &= ~CYGARC_REG_SCI_SCSSR_FER;
        sh_serial_error_fer++;
    }
    if (_ssr & CYGARC_REG_SCI_SCSSR_PER) {
        _ssr2 &= ~CYGARC_REG_SCI_SCSSR_PER;
        sh_serial_error_per++;
    }
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSSR, _ssr2);

    HAL_READ_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
    _scr |= CYGARC_REG_SCI_SCSCR_RIE;       // unmask rx interrupts
    HAL_WRITE_UINT8(sh_chan->ctrl_base+SCI_SCSCR, _scr);
}

#endif // ifdef CYGDAT_IO_SERIAL_SH_SCI_INL