Here are just samples out of much longer data. It does NOT repeat every samples on real chip and I wasnt able to find. I only put it here because its better than nothing and perhaps. Note that due to the way the LFO output is calculated it is quite.
To be exact:. YMResetChip i ;. YMWriteReg num, i, 0 ;. The 'rate' is calculated from following formula example on decay rate :. Four MSBs of the 'rate' above are the 'main' rate from 00 to Two LSBs of the 'rate' above are the value 'x' the shape type. NOTE: A 'sample' in the description below is actually 3 output samples,. Single '-' minus character in the diagrams below represents one sample. Shapes for rates 11 x look like this:.
I have an interesting observation. When plugging the YM chip into our SFG module clone with the patched 05 bios, the music plays much slower.
Could be our YM implementaion's effect of course. Or maybe there are more differences between those chips than we see. On the YM it seems bit 7 of timer B has a different function. The timer resolution is also reduced by 1 bit. Giving it the YM value will result in double the timer period. In other words;. Also, I just noticed the - CLKB part of the formula; this means that there is no special function to bit 7, it simply feeds in a 1 because the period value is negated. Posted the info on the MAP.
Also, a small side note from me, looking at that ROM file for the upgrade, the changes are pretty targeted and tidy, and testify knowledge about the specifics of the YM which is otherwise undocumented and supposedly was never generally available.
This could be used, for example, in a guitar solo. Unfortunately, these timers do not cause interrupts - they must be read by the software to determine if they have finished counting. Page 5 - original - top. These operators may be arranged in eight different configurations, called "algorithms".
Following is a diagram of the algorithms. Page 6 - original - top. Page 7 - original - top. The remainder of the registers apply to a single FM channel, or to an operator in that channel.
Registers that refer to the channel as a whole are:. Registers that refer to each operator make up the remainder.
The four operator's connections are determined by the algorithm used, but the envelope is always specified individually for each operator. In the case of FM channels 3 and 6, the frequency may be specified individually for each operator. Page 8 - original - top.
The sound starts when the key is depressed, a process called 'key on'. The sound has an attack, a strong primary decay, followed by a slow secondary decay. The sound continues this secondary decay until the key is released, a process called 'key off'. The sound then begins a rapid final decay, representing for example a piano note after the key has been released and the damper has come down on the strings. The envelope is represented by the above amplitudes and angles, and a few supplementary registers.
Used in the above diagram are:. Page 9 - original - top. The YM may be accessed from either the or the Z In both cases, however, the bus is only 8 bits wide. These will be referred to as to To write to Part I, write the 8 bit address to and the data to To write to Part II, write the 8-bit address to and the data to Delay until bit 7 returns to 0.
CAUTION: in the case of registers that are "ganged together" to form a longer number, for example the bit Timer A value or the bit frequencies, write the high register first. Page 10 - original - top. Page 11 - original - top. It is triply enabled, as there is:. If the LFO is desired, enable it by register 22H. Next, select which channels will be affected by the LFO, to what degree, and whether their amplitude or frequency is affected, by setting registers B4-B6H.
Page 12 - original - top. Registers 24H and 25H are ganged together to form bit Timer A , with register 25H containing the least significant bits.
They should be set in the order 24H, 25H. The timer lasts:. Register 27H controls the software timers and the Channel 3 and 6 mode , two entirely separate items. A normal channel's operators use offsets of integral multiples of a single frequency.
In special mode, each operator has an entirely separate frequency. Channel 3 operator 1's frequency is in registers A2 and A6. Page 13 - original - top.
0コメント