but I think you mean to shift out a byte on an I/O ?

void send_char (void)
{
unsigned char n;
for (n=0; n<8; n++) //send 8 BIT
{
if (dsp_char_out & (0x80 >> n)) // MSB first
{
_DATA |= 0x01; // HIGH Level @ IO
}
else
{
_DATA &= ~0x01; // LOW Level @ IO
}
shift_clock(); // generate a high to low transition
}
}

A Byte in dsp_char_out will be shifted out MSB first.
If you need LSB first try:

if (dsp_char_out & (0x01 << n))

Is that what you are looking for ??