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Iridium 9523/9523N L-Band Tra nsce iver Integrator Devel opme nt Guide
Revis ion 7 .4
3.3
PCM Digital Audio
The Iridium Core 9523/9523N has two PCM digital audio ports, though only one of these can be in use at any
time. The active port is selected using the AT+CAR command. This setup allows the FA board to provide two
parallel audio paths and switch between them through software instead of hardware. The two ports have
identical signals and timing, as shown in Figure 11. The PCM clock and sync signals are outputs from the
Iridium Core 9523/9523N.
The PCM clock signal has a frequency of 2048 kHz with an accuracy of 1 ppm, but it is derived from an internal
clock source by a fractional divider so each clock high period and low period is either 238.1 ns or 297.6 ns.
The PCM clock, sync and data signal outputs are all timed from the same internal clock and are skewed by less
than 1 ns (at equal load).
The PCM data input has set-up and hold time requirements of 30 ns with respect to the falling edge of the PCM
clock signal.
The two PCM ports were originally intended to be connected to a voice source/sink via a codec (such as the
Texas Instruments TLV320AIC1110) for analog audio and directly for digital audio, but there is no need to use
them in this way.
PCM clock
PCM sy nc
PCM output
PCM input
3.3.1
Port 1
Port 1 has the following signal pins:
Note: the data signal names on Port 1 are defined from the point of view of an externally connected codec.
Proprietary & Confidential Information
Distribution of guide restricted to product dev elopers only . Inf ormation contained in this guide is subject to change without notice.
.
Figure 11 - PCM waveform diagram
2
1 ( msb )
1 ( msb )
2
Table 13: PCM Port 1 Signals
Signal function
PCM clock output
CODEC_PCMCLK
PCM sync output
CODEC_PCMSYNC
PCM data output
CODEC_PCMIN
PCM data input
CODEC_PCMOUT
3
4
4
3
Signal name
16 ( lsb )
15
15
16 ( lsb )
30
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