void OPL_WriteRegister(int reg, int value)
{
int i;
OPL_WritePort(OPL_REGISTER_PORT, reg);
// For timing, read the register port six times after writing the
// register number to cause the appropriate delay
for (i=0; i<6; ++i)
{
// An oddity of the Doom OPL code: at startup initialization,
// the spacing here is performed by reading from the register
// port; after initialization, the data port is read, instead.
if (init_stage_reg_writes)
{
OPL_ReadPort(OPL_REGISTER_PORT);
}
else
{
OPL_ReadPort(OPL_DATA_PORT);
}
}
OPL_WritePort(OPL_DATA_PORT, value);
// Read the register port 24 times after writing the value to
// cause the appropriate delay
for (i=0; i<24; ++i)
{
OPL_ReadStatus();
}
}
void WriteReg(unsigned int reg, unsigned int val)
{
int i;
// This was recorded from an OPL2, but we are probably playing
// back on an OPL3, so we need to enable the original OPL2
// channels. Doom does this already, but other games don't.
if ((reg & 0xf0) == OPL_REGS_FEEDBACK)
{
val |= 0x30;
}
OPL_WritePort(OPL_REGISTER_PORT, reg);
for (i=0; i<6; ++i)
{
OPL_ReadPort(OPL_REGISTER_PORT);
}
OPL_WritePort(OPL_DATA_PORT, val);
for (i=0; i<35; ++i)
{
OPL_ReadPort(OPL_REGISTER_PORT);
}
}
unsigned int OPL_ReadStatus(void)
{
return OPL_ReadPort(OPL_REGISTER_PORT);
}
