PXD20RM Datasheet, PDF (1392/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Table 39-43. Work flow of generating a sequence of notes by one channel (continued)
11. Configure the SGM (interrupt, clocking ...)
12. check the FIFO status. If the fifo is Full, set the
SGMCTL.SOGCHx to enable another DDS
generation of another note sequence.
...
...
Note: * If user want to use the same wavetable for generating another note sequence, step 6-10 can be skipped.
39.9.2.2 Polyphonic alarm sound
39.9.2.2.1 Description
In this use case the application generates a repetitive polyphonic sound with a blank period in-between.
The duration of a single sound and the inter-note no-output time can be controlled by the ASR envelope.
The duration of the repetition can be programmed in the number of the note pulses.
39.9.2.2.2 SGM functionality
A typical/simple example could be:
• Every channel generates one note periodically. Four channels generate four different notes.
• CPU only needs to configure the SGM once.
• All four channels can be configured simultaneously or in some sequence.
• The number of the note pulses are programmable to control the entire duration.
The figures below show an simple example of polyphonic alarm sound.
Figure 39-66. Channel 0
39-68
Figure 39-67. Channel 1
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor