PXD20RM Datasheet, PDF (1364/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Table 39-39. I2SST field descriptions
Field
31
TSFE
31-26
25
FOF
24
FUF
18
CPL
15-8
7-4
FIFOST
3-1
0
BSY
Description
I2S transfer error.
If the I2S FIFO is empty but the I2S requests data then transfer error interrupt will be raised.
Reserved.
I2S FIFO Overflow.
Interrupt indicating the FIFO overflow. The I2S soft reset can clear this flag.
I2S FIFO Underflow.
Interrupt indicating the FIFO underflow. The I2S soft reset can clear this flag.
I2S complete
Interrupt indicating all data is transferred after receiving end of sequence from the SGM.
Reserved.
FIFO Status.
This field specifies the amount of data currently residing in the I2S FIFO. Cleared on soft reset, or when the I2S
FIFO gets emptied.
Reserved.
I2S Busy.
The I2S interface is busy. Cleared on soft reset or when module completes outputing data.
39.7 Functional description
The Sound Generator Module creates sound by clocking PCM sound samples out of up to four sound
source channels, mixing these together and sending the output to either a mono PWM output or to a stereo
I2S interface. The sound channels can operate in one of two modes depending on whether a wavetable
(DDS mode) or complete PCM stream (wave) is required. DDS mode includes a volume envelope that
shapes the playback of the wavetable. The volume in Wave mode is determined by the volume set in the
mixer for that channel.
39.7.1 Wave mode
In Wave mode, the PCM data is stored in memory external to the SGM (for example RAM or flash). Each
sample is fetched using the eDMA then fed to the SGM which promotes it to 16 bits per sample using its
Sample Format Converter (SFC). Samples should be in two’s complement signed format. The channel
FIFO is used to buffer the incoming data and then deliver the samples at the required clock rate to the
mixer. As a sample is fetched from the FIFO and played by the channel its location in the FIFO will be
replaced by a newer incoming sample.
There are two options for playback:
• Single Shot Mode. In this mode the channel “plays” the entire source wave once. The duration of
the playback is controlled by the Playback Timing Configuration register (Section 39.6.2.11,
PlayBack Timing Configuration Register for Channel 3(PTCCH3)) which determines the number
39-40
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor