// timer callback at VCK low edge on MSM5205 (at rising edge on MSM6585)
void update_adpcm()
{
int val;
int new_signal;
// callback user handler and latch next data
if (!m_vck_legacy_cb.isnull())
{
m_vck_legacy_cb.op(1);
}
// reset check at last hiedge of VCK
if (m_reset)
{
new_signal = 0;
m_step = 0;
}
else
{
/* update signal */
/* !! MSM5205 has internal 12bit decoding, signal width is 0 to 8191 !! */
val = m_data;
new_signal = m_signal + m_diff_lookup[m_step * 16 + (val & 15)];
if (new_signal > 2047)
{
new_signal = 2047;
}
else if (new_signal < -2048)
{
new_signal = -2048;
}
m_step += index_shift[val & 7];
if (m_step > 48)
{
m_step = 48;
}
else if (m_step < 0)
{
m_step = 0;
}
}
/* update when signal changed */
if (m_signal != new_signal)
{
m_stream.update();
m_signal = new_signal;
}
}
