PXD20RM Datasheet, PDF (1389/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

39.9.2.1 Polyphonic sound
39.9.2.1.1 Description
In this use case the application generates sequences of notes on each channel. When mixed, these generate
a polyphonic sound. For every individual note, the duration is defined by the configurable ASR envelope.
39.9.2.1.2 SGM functionality
The SGM needs to be configured with the following information:
• Wavetable
• ASR envelope
• Frequencies of every individual notes, which are defined by the timing configuration of the channel
To generate a sequence of notes using a single channel, enable the interrupt on reaching the configurable
target volume level of the release phase. The frequency of each note should be configured by software.
All 4 channels can be configured simultaneously or in some sequence. When all 4 channels are mixed a
polyphonic sound is generated.
The figures below shows an example of generating/mixing polyphonic sound. And Table 1-6 shows a work
flow of generating a sequence of notes by one channel.
1^st Note
2^nd Note
3^rd Note
4^th Note
5^th Note
1^st Note
2^nd Note
Figure 39-61. Channel 0
3^rd Note 4^th Note 5^th Note 6^th Note 7^th Note
8^th Note
9^th Note
Figure 39-62. Channel 1
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
39-65