ymfm
ymfm copied to clipboard
aaronsgiles
OPZ can not handle key on/off properly
The following code in the opz_registers::write(uint16_t, uint8_t, uint32_t, uint32_t) is not correct.
// handle writes to the key on index
if ((index & 0xf8) == 0x20 && bitfield(index, 0, 3) == bitfield(m_regdata[0x08], 0, 3))
OPZ does not see the 0x08 register for key on/off . So. change it like the following.
// handle writes to the key on index
if ((index & 0xf8) == 0x20)
Sorry, this info is not correct.
The following URL information is not perfect. http://sr4.sakura.ne.jp/fmsound/opz.html
・Panpot, Key on/off register is same as OPM/OPP. ・Ch volume register(#0 -#7) does not exist on OPZ.
What is the evidence for this change? The document referenced is not correct.
The current implementation is based on actual behavior of what the TX-81Z writes in emulation. Until I see strong evidence of different behavior that is still compatible with the way the TX-81Z programs the chip, I'm reluctant to make any changes here.
We do not have an application manual of YM2414.
So, I've contact FITOM author ”madscient” to check correctly implementing of the OPZ.
Do you know FITOM project? https://sites.google.com/site/fitomproject/
He said that "I checked the registers one by one and created a FITOM. My implementing is correct."
See this thread. https://twitter.com/SNDR_SNDL/status/1445013048628944899
I think the behavior of the TX-81Z is due to the software sound driver.
He said that this source contains OPZ driver that is derived from OPM and the driver can drive OPZ properly.
https://github.com/madscient/FITOMApp/blob/primary/FITOMApp/OPM.cpp
He created a document about YM2414 (Tentative ver)
https://sites.google.com/site/undocumentedsoundchips/yamaha/ym2414
My friend replaced a chip from YM2151 to YM2414. https://twitter.com/sdhizumi/status/1453924274989793280
YM2414 can output LR ch properly by YM2151 driver except MONO ch.
If that is a legitimate (true) YM2414, then it is possible that key on/off can also be triggered like a YM2151. I will be interested to see if the YM2414 shown works in the TX-81Z.
The firmware of the TX-81Z uses the documented sequence in my code to send key on/off, and not the YM2151 way. If this is true, then ymfm will need to be updated to support both ways.
FYI: Here is an Output Level algorithm of TX81Z(not YM2414) sound driver.
https://nornand.hatenablog.com/entry/2020/11/21/201911