User's Manual

39
10
-18
11
-14.5
12
-12
13
-8.5
14
-6
15
-2.5
Table 14: DAC digital gain rate selection
The DAC analogue amplifier has a programmable gain with seven individual 3dB steps. The overall gain
control of the DAC is controlled by a VM function. This setting is a combined function of the digital and
analogue amplifier settings, therefore, for a 1V rms nominal digital output signal from the digital gain
stage of the DAC, the following approximate output values of the analogue amplifier of the DAC can be
expected:
Analogue Gain Setting
DAC Gain Setting (dB)
7
3
6
0
5
-3
4
-6
3
-9
2
-12
1
-15
0
-18
Table 15: DAC analogue gain rate selection
7.2.3 IEC 60958 Interface
The IEC 60958 interface is a digital audio interface that uses bi-phase coding to minimize the DC
content of the transmitted signal and allows the receiver to decode the clock information from the
transmitted signal. The IEC 60958 specification is based on the two industry standards AES/EBU and
the Sony and Philips interface specification SPDIF. The interface is compatible with IEC 60958-1, IEC
60958-3 and IEC 60958-4.
The SPDIF interface signals are SPDIF_IN and SPDIF_OUT and are shared on the PCM interface pins.
The input and output stages of the SPDIF pins can interface either to a 75Ω Coaxial cable with an RCA
connector, see Figure 15, or there is an option to use an optical link that uses Toslink optical
components, see Figure 16.
NOTE: the S/PDIF interface is not recommended for use at this time due to an issue with the low-
level BlueCore05-MM firmware revision in use by iWRAP. The audio quality suffers because the
left and right channels get out of sync.
Figure 15: Example circuit for SPDIF interface (Co-Axial)