
Phase/Frequency Determination and Xtrim Function
MOTOROLA
Audio Functions
17-37
Operation is as follows:
–
If PDIR2 is full and DMAConfig(1) is set to ‘0’, Dma1Req is activated.
–
If PDIR2 is full and DMAConfig(0) is set to ‘0’, DMA0req is activated.
–
If the FIFO connected to PDOR3 is empty, and DMAConfig(1) is set ‘1’, Dma1Req is
activated.
–
If the FIFO connected to PDOR3 is empty, and DMAConfig(0) is set to ‘1’, DMA0req is
activated.
Both DMA1req and DMA0req can be routed to DMA channel 0 or DMA channel 1. For details, see
description of ColdFire DMA controller.
17.6
PHASE/FREQUENCY DETERMINATION AND XTRIM FUNCTION
These features are necessary so that users can determine when a software sample rate convertor should
be enabled and provide the necessary control to steer the sample rate convertor clock (when the incoming
sample rate is other then 44.1 Khz).
In addition, users can also utilize this function to determine when the incoming IEC958 clock does not
match the phase of the Xtal oscillator and use the XTRIM function to trim the external oscillator to match
(within a 150ppm range). Typically, when the IEC958 input is being used, the xtal requires trimming to
match but this is only when the source is completely external to the application.
When the source is internal to the application, such as from a CD player controlled by the MCF5249, then
the input sample rate does not need to match the output sample rate, so they can be asynchronous. When
FIFO under-run or over-run occurs, request that the data lost is re-read by the system.
17.6.1
INCOMING SOURCE FREQUENCY MEASUREMENT
The PLL maintaining phase relation between incoming source signal and internal signal is mainly digital. It
is necessary, however, to measure phase/frequency of the incoming signal in relationship with the crystal
Table 17-35 DMA Config Register Address
BITS
7
6
5
4
3
2
1
0
FIELD
DMA1REQ
DMA0REQ
RESET
00
R/W
ADDR
MBAR2 + 0X9F
Table 17-36 DMA Config Bit Descriptions
BIT NAME
DESCRIPTION
NOTE
S
DMA1REQ
0 = PDIR2
1 = PDOR3
1, 2, 3
DMA0REQ
0 = PDIR2
1 = PDOR3
1, 2, 3
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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