PXD20RM Datasheet, PDF (1365/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

of samples in the source wave. See Figure • for a simple example where the source wave consists
of 5 samples.
Figure 39-36. Single shot mode playback
Channel clock
Sample output
S0
S1 S2 S3 S4
• Repeat Mode. In this mode the channel “plays” the entire source wave then waits for a deadtime
(Section 39.6.2.12, Dead Time Configuration Register for Channel 3(DTCCH3)) during which it
produces samples of value 0 then “plays” the entire wave again. The number of repeats is
programmable in the Repeat Number Register (Section 39.6.2.13, Repeat Number Configuration
Register for Channel 3(RNCCH3)). In the last iteration, the deadtime duration is removed and the
repeat finishes at the end of playback duration. Endless repetition can be produced by setting the
repeat number to all 0. See Figure for an example where the five sample source wave is repeated
three times.
Figure 39-37. Repeat mode playback
S0 S1S2S3 S4 0x0000 S0S1 S2 S3 S4 0x0000 S0 S1 S2 S3 S4
Playback=5
Playback=5
Playback=5
Deadtime=3
Deadtime=3
Repeat number=3
The input FIFO (25616 bit) for each channel is used to buffer the incoming PCM audio sample stream.
See Figure 39-38. The status of the FIFO such as overflow and underflow is reported in the FIFO and
DMA status register (Section 39.6.2.27, SGM Interrupt Status Register for FIFO and DMA (SGMISFD))
which can also raise interrupts if required. Configure the interrupt requirements using the FIFO and DMA
interrupt control register (Section 39.6.2.25, SGM Interrupt Control Register for FIFO and DMA
(SGMICFD)).
NOTE
For correct operation the eDMA Transfer Descriptor must match the
playback length of the wave.
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
39-41