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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001
Manual part no: DOC1241121A1
Page 90
Document No: OS-MA-A0124-112.1A1
Contact
dCS
on + 44 1799 531 999 email to: more@dcsltd.co.uk
(inside the UK replace + 44 with 0) web site: www.dcsltd.co.uk
SDIF-2 Message Handling
The SDIF-2 interface is a 4 wire NRZ interface - so the DC level on each signal
line may not be constant. It contains 20 bits of audio data and has a block
structure of 256 stereo samples, rather than the 192 of AES/EBU. There are 8
bits of message per channel per sample - with a further 3 bits being used for an
"illegal code" based sync code. Of the 8 bits per sample, the 8 in the first
sample are reserved for system messaging, and the rest are for User
messages.
The 4 wires are:
Ground return
Left Channel
Right Channel
Wordclock
The sync codes enable data recovery without the word clock, if necessary, but
with the number of data formats in current operation, this method of locking is
strongly discouraged.
The SDIF-2 message is given in the table following. The dCS 974
implementation sets all bits of the User message to "0".
DESCRIPTION Definition Default
Message
Undefined 0000 0xxx 0000 0xxx
Emphasis
No emphasis
Emphasis (15µsec, 50µsec)
xxxx x00x
xxxx x01x
xxxx x00x
Dubbing Prohibit
Dubbing allowed
Dubbing inhibited
xxxx xxx0
xxxx xxx1
xxxx xxx0
Block Code
Start of block
Not start of block
xxxx xxxx 1...
xxxx xxxx 0...
as required
as required
Table 15 - SDIF-2 Message Table
SDIF-3 Message Handling
At present, no messaging is implemented in SDIF-3.