Altera DisplayPort MegaCore Function - Manual (Page 33)

Table 4-10: Audio Signals
Signal Comments
txN_audio_clk Audio interface input clock.
txN_audio_valid Audio input data valid.
txN_audio_mute When asserted, indicates that audio muting is enabled.
txN_audio_lpcm_data[m*32-
1:0]
m-channel, 32-bit audio sample data.
Figure 4-9: Audio Sample Data Bits
The packing format uses an IEC-60958-type encoding.
7 B3 0 7 B2 0 7 B1 0 7 B0 0
31 24 23 16 15 8 7 0
SP R PR P C U V MSB Audio Sample Word [23:0] LSB
31 29 28 25 24 30 27 26 23 0
Table 4-11: Audio Sample Bit Field Definitions
Bit Name Bit Position Description
Audio sample
word
Byte 2, bits 7:0
Byte 1, bits 7:0
Byte 0, bits 7:0 Audio data. The data content depends on the audio coding type. For
LPCM audio, the audio most significant bit (MSB) is placed in byte
2, bit 7. If the audio data size is less than 24 bits, unused least signifi‐
cant bits (LSB) must be zero padded.
V Byte 3, bit 0 Validity flag.
U Byte 3, bit 1 User bit.
C Byte 3, bit 2 Channel status.
P Byte 3, bit 3 Parity bit.
PR Byte 3, bits 4 - 5 Preamble code and its correspondence with IEC-60958 preamble:
00: Subframe 1 and start of the audio block (11101000 preamble)
01: Subframe1 (1110010 preamble)
10: Subframe 2 (1110100 preamble)
R Byte3, bit 6 Reserved bit; must be 0.
UG-01131
2015.05.04
Audio Interface 4-17
DisplayPort Source Altera Corporation
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