SYSTEM CONNECTOR INTERFACE
35
LZT 123 8020 R1A
5.8.1
PCM Data Format
All of the radio device’s PCM signals, including signals between
its CODEC and DSP conform to the PCM data I/O format of the
industry standard DSP from Texas Instruments.
PCMCLK (bit clock) and PCMSYNC (frame synchronisation)
are both generated by the DSP within the radio device.
The DSP within the radio device is the master therefore all
external PCM clocks and data from external devices must be
synchronized to it
13-Bit PCM Mode
Bit
Contents
D15 to D14
Equal to D13
D13 to D1
Two's complement of the 13-bit PCM
D0
LSB, not used
The radio device implements 13-bit PCM with the 13-bit data
embedded in a 16-bit word within a 24-bit frame (see Figure
5.8). Each PCM word contains 16-bits: D0 to D15. D13 to D1 is
the two’s complement value of the 13-bit PCM, with D13 as the
sign bit. D14 and D15 are always set to be equivalent with D13.
D0, the LSB, is not used as shown in Figure 5.7 below.
Figure 5.7 16-bit data word format
16-Bit PCM Mode
Bit
Contents
D15 - D0
Two's complement
The frame format is equal to the one shown in Figure 5.7, but
with D15, D14 and D0 filled with significant bits. D15 to D0 is
the two’s complement value of the 16-bit PCM with bit 15 as the
sign bit.
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