PSB7238 SIEMENS [Siemens Semiconductor Group], PSB7238 Datasheet - Page 177

• Manufacturer Part Number: PSB7238
• Description: Joint Audio Decoder-Encoder - Multimode
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

clock and the audio codec’s clock is acceptable to the JADE and should be aurally
imperceptible. In the following this will be called the long term skew.
In addition to the long term skew, the JADE can correct for short term variances using
an internal buffer mechanism. This allows single SIO periods to be 10 ms
The full definition is as follows:
Long term SIO period
Short term SIO period
Duration of n consecutive SIO periods:
The basic clock for the definition of [ms] is the frame sync signal of the uncompressed
audio interface.
The timing of the JADE firmware is controlled by the video processor, which generates
an interrupt every 10 ms at the SIO line. The JADE then starts generating a number of
frame sync signals at RFS and TFS, depending on the length of the data packet that has
to be exchanged. The RFS and TFS bursts are asynchronously, i.e. the RFS burst starts
about 16 frame syncs before the TFS. After data packet transfer the JADE waits for the
next SIO interrupt.
Note: During startup procedure the uncompressed interface (IOM) must be setup before
Due to small differences in the clock of the video processor and the audio output, the
JADE is able to add two uncompressed audio samples every 10 ms. That means, a skew
of about 2.5% (
Note: For maximum audio quality it is recommended to keep the skew between the
Semiconductor Group
the Serial Audio Interface is started, i.e. the FSC and DCL signals must be stable
before the first 10 ms interrupt is generated by the video processor.
IOM-2 and the SIO time base as small as possible, i.e. to adjust T
definition as close to 10 ms as possible. In an application with the VCP from 8 8
(formerly IIT) like in the Siemens/8x8 demonstration board design, the SIO
interrupt period is locked to the IOM-2 time base after a call is setup, so no
compensation on the uncompressed audio needs to be done by the JADE any
more. This ensures the maximum possible audio quality.
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Data Sheet 1998-07-01
Firmware Features
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in the above
PSB 7238
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