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Posted Sun Feb 20, 2011 10:04 PM
Posted Mon Feb 21, 2011 12:13 AM
Posted Mon Feb 21, 2011 9:58 AM
The YM2151 datasheet is here :-
If anybody finds a good tracker (like RMT on the A8s) that I can add to my list of 7800 projects then let me know.
Posted Mon Feb 21, 2011 10:40 AM
Posted Mon Feb 21, 2011 11:06 AM
I don't know the answer to your question but I suspect that changing 8 instruments, 50-60 times per second would be quite a complex music track. Anything complex is going to have CPU overhead. So, if it was me I'd probably play tracks like that on static screens like the title page or high score chart where CPU cycle time isn't such an issue.
Posted Mon Feb 21, 2011 11:42 AM
50-60 times per second would be quite a complex music track.
Edited by tep392, Mon Feb 21, 2011 11:52 AM.
Posted Mon Feb 21, 2011 12:27 PM
Huh? Don't think I suggested that.
Is a glitch in a single frame invisible? If so, then I won't worry too much.
Posted Mon Feb 21, 2011 1:17 PM
Posted Mon Feb 21, 2011 1:20 PM
Edited by tep392, Mon Feb 21, 2011 1:21 PM.
Posted Mon Feb 21, 2011 4:19 PM
Wow - that's a MASSIVE upgrade over the TIA The SDI music is really nice.
For those who don't know, this is what the YM2151 is capable of:
Posted Mon Feb 21, 2011 11:55 PM
The YM2151 user manual indicates it will take up to 68 clocks (at 3.5 mhz) for a write to the chip to be processed. This works out to be about 35 clocks of the 6502. To write a byte to the chip requires an address write and a data write. I don't know if this wait apply's to both.
My concern is that I will waste a lot of clock cycles waiting to write to the sound processor. For each note that I start, I need to write a note value and key on the channel. This means 4 writes (2 * address+data) for each note. In an 8 channel tune, this can add up fast. But my biggest concern is when I need to write the "instrument" data to setup a channel. Each channel has 28 bytes of parameter data to define. 28 bytes * 2 writes per byte * 35 clocks is a whopping 1960 clocks of the 6502. That's a lot of time to waste while waiting for the status bit to toggle.
Posted Tue Feb 22, 2011 6:58 AM
Posted Tue Feb 22, 2011 7:27 AM
Would be almost worth having the XM have a small FIFO to drive the YM chip with to allow rapid stuffing of registers..
Posted Wed Mar 23, 2011 1:35 PM
Posted Wed Mar 23, 2011 4:29 PM
although I am not a musician,I am interested in the YM2151 from a technical point of view.Many registers to experiment with.
I would like to add that the YAMAHA CX5M MSX computer had an extension with MIDI/KEYBOARD and a YM2151 stereo output.You can
find things about it here: http://www.cx5m.net/techn.htm and here: http://home.online.n...html#midiaccess
for example.The roms of the extension are also available and can be used with the bluemsx emulator (but without music!).
The SFG-05 rom has 46 Programmed Instruments.It is not difficult to find them in the rom ($3680..$3F80) but I have not
found out the format of the data except for the instrument name.Some Z80 disassembly has to be done,but it is not strait forward.
They make heavy use of IRQs in IM1 and IM2 and I think they also use dynamic jump tables.It is not easy but with the breakpoint feature
of the emulator some things can be found...
This could be some starting point to have some data to play with.The service manuals of the CX5M are also available online.
They also never poll the YM2151 directly,it is somehow in all this IRQ handling! But they also have code that writes addr and data
in the registers without waiting.Maybe this is depending on the register that is written to.I unfortunately do not own one CX5M but
bought a YM2151/YM3012 and NJM4456 to try to tinker a bit.The CX5M manuals have the circuit diagrams inside.
I am also interested in the implementation inside the XM:
- What will be the operating frequency of the YM ? (YAMAHA recommends 3,5795MHz)
- The YM has two visible register,where will they be in the address range ?
- Will the YM use IRQs ? if so will they be shared with the pokey ?
- Will the XM use the YM3012 (stereo) or the YM3014 (mono) D/A converter ?
- Will it have separate stereo outputs (if stereo) or will it mixed onto the audio pin of the cart ?
Thank you for reading and your opinion,
Posted Wed Mar 23, 2011 8:02 PM
Posted Thu Mar 24, 2011 6:00 AM
Posted Mon May 16, 2011 2:11 PM
Posted Thu May 19, 2011 3:32 PM
Edited by philipj, Thu May 19, 2011 3:59 PM.
Posted Thu May 19, 2011 9:58 PM
Posted Thu May 19, 2011 10:43 PM
Posted Fri May 20, 2011 6:16 AM
This is going to give the system excellent sound capabilities.
Posted Fri May 20, 2011 7:41 AM
Edited by philipj, Fri May 20, 2011 8:05 AM.
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