GS9023 datasheet(21/33 Pages) ETC

21 / 33 page

GENNUM CORPORATION

522 - 45 - 05

Control Code Output

In the non-AES/EBU output formats, the V, U and C bits are

output separately from the audio data stream. The bits are

output respectively to the VFLA/B, UDA/B and CSA/B pins

according to the channel pair to which they belong and

change state on the rising edge of WCOUT. The SAFA/B

output pins are set to HIGH for one audio frame out of 192

frames to mark the start of a block. In the AES/EBU audio

output format, the respective pins are not used.

Detection of Audio Packets

The GS9023 can demultiplex up to four audio channels of

an audio group. The audio group (Audio packet data ID) for

each device is configured in “AD20ID[3:0]” of Host

Interface Register #3h. When the corresponding audio

packets are found on the active video line, the GS9023 sets

the

respective

“CHACT(4-1)”

bits

Host

Interface

on the active video line, the “CHACT(4-1)” bits are set LOW.

By connecting four GS9023 devices in parallel, it is

possible to demultiplex up to 16 audio channels in a

component video signal as shown in Figure 19. On power

up, audio group 1 is selected by default.

Detection of Extended Audio Packets

The GS9023 can demultiplex 20 or 24 bit audio samples.

For 24 bit audio samples, the 20 MSBs of a 24 bit audio

sample are contained in the audio data packets and the 4

LSBs are contained in an extended audio data packet as

defined in SMPTE 272. The audio group (Extended packet

data ID) for each device is configured in “AD4ID[3:0]” of

Host Interface Register #3h. When the corresponding

extended audio packets are detected on the active video

stream, the GS9023 sets the AUXEN pin and the “A4ON” bit

of Host Interface Register #1h to HIGH. If no corresponding

extended audio packets are found on the active video line,

the AUXEN pin and “A4ON” bit are set to LOW. On power

up, audio group 1 extended audio packets are selected by

default.

Detection of Audio Control Packets

The audio group (Audio control packet data ID) for each

device is configured in “ACID[3:0]” of Host Interface

designated video lines (

see Table 6), the “ACON” bit of

Host Interface Register #1h is set. The corresponding Audio

control

parameters

are

stored

Host

Interface

Registers #Ah, #Bh, #Ch and #Dh. If an audio control

packet is not detected or found in non-designated video

lines, “ACON” is set to LOW. However, the information in the

audio control packets found in non-designated lines is

considered valid and is stored in Host Interface Registers

#Ah, #Bh, #Ch and #Dh. On power up, audio group 1 audio

control packets are selected by default.

Detection and Output of Arbitrary Data Packets

The GS9023 is capable of demultiplexing arbitrary data

packets according to SMPTE 291M. There are no limitations

on the number of packets that can be demultiplexed and

the packets can be located outside of the vertical blanking

interval (VBI).

The arbitrary data packet data ID is configured in

PKTID[7:0] of Host Interface Register #5h. When the

configured ID is detected in the active video or HANC area,

data on the PKT[8:0] pins is clocked out on the rising edge

of PCLK. The GS9023 sets the PKTEN output pin HIGH,

when the data at the PKT[8:0] outputs is valid. PKTEN is set

LOW when the last user data word (UDW) is output from

PKT[8:0]. Figure 13 shows the output timing.

Fig. 13: Arbitrary Data Output Timing Diagram

Error Detection

The GS9023 provides error status information in Host

Interface Registers #7h, #8h and #9h as described in Table

15. Register #7 contains error information on audio

sampling and CRC conditions. Register #8 contains error

information on audio packet data block number and data

count. Register #9 contains error information on Control

packets. Errors are cleared when the respective Host

Interface Register is read.

PCLK (I)

PKTEN (O)

PKT[8:0] (O)

Valid data

NOTE: 1 - The ancillary data flag, ADF, is one word in composite systems (ANSI/SMPTE 259M)

and three words in component systems (ANSI/SMPTE 125M).

1 clk

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