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MUSIC SYNTHESIS SOFTWARE<br />

677<br />

Fig. 18-11. Percussive sound model<br />

HIGH BYTE<br />

LOW BYTE<br />

MNEMONIC<br />

BLOCK<br />

ADDRESS<br />

ACTIVITY<br />

FLAGS<br />

SOUND 10<br />

SNDID<br />

+2<br />

+4<br />

+ 6<br />

+ 8<br />

+ 10<br />

+ 12<br />

+ 14<br />

+ 16<br />

+ 18<br />

+ 20<br />

+ 22<br />

+ 24<br />

+ 26<br />

+ 28<br />

BANDPASS FILTER F<br />

BANDPASS FILTER Q<br />

MULTIMODE FILTER F<br />

MULTIMODE FILTER Q<br />

FILTER MODE<br />

DAMPED SINE AMP<br />

FILTERED NOISE AMP<br />

OVERALL AMP<br />

ADDRESS OF SAMPLE BUFF<br />

STORAGE FOR BANDPASS<br />

FILTER<br />

STORAGE FOR MULTIMODE<br />

FILTER<br />

NOISE REGISTER<br />

RESNF<br />

RESNQ<br />

MMFF<br />

MMFQ<br />

MMFM<br />

RESNAM<br />

MMFAM<br />

AMP<br />

SMPBFA<br />

RESNDl<br />

RESND2<br />

MMFDl<br />

MMFD2<br />

NOISE<br />

+ 30<br />

UNUSED<br />

Fig. 18-12. Sound control block for percussion generator<br />

The sound control block for percussive sounds is shown in Fig. 18-12.<br />

The data elements in the control block should be self-explanatory. Note that<br />

all but two bytes <strong>of</strong> the block are used and that many <strong>of</strong> them simply describe<br />

the percussive timbre, which is (:onstant. In the tone generator control block,<br />

the actual waveform was stored elsewhere and a pointer to the information was<br />

given. This could also be done with the percussive generator and thus free up<br />

10 bytes in its sound control block, although it was not.<br />

Figure 18-13 is a flowchart <strong>of</strong> the major operations performed by the<br />

Level 1 percussion routine. Note that each half <strong>of</strong> the percussive sound<br />

model is checked for activity before computing the 30 samples. This saves<br />

considerable time when only half <strong>of</strong> the model is needed for simple percussive<br />

sounds.

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