Table 1 - Agens, And What Can Be Programmed - DCS 992 User Manual

dCS 992 User Manual
dCS Ltd
TCXOs and AGENs
4
There are some restrictions on independence to do with 32kS/s operations
Manual part no: DOC063992 iss 2A1
Contact on + 44 1799 531 999
dCS
(inside the UK replace + 44 with 0)
The unit contains several TCXOs, only one of which is active at any time. The
active one is temperature compensated and controlled by a DSP. Its output is
routed to four independent
output is always connected to AGEN 1 – all other AES3 outputs
may be connected to any AGEN – they can all be driven by AGEN 1, or they can
have one each, or anything in between. AGENs can be programmed for sample
rate, output phase, AES3 message content, and (in the case of AGEN 1) the
audio signal it carries.
AGEN 1 is special – its output sample rate determines which TCXO is used. It
will have the lowest jitter.
multiples or sub-multiples of AGEN 1's, then they have negligible jitter.
however, they are set to sample rates with complex relationships to AGEN 1,
then the DDS used to generate them will dither the transition times, generating
jitter. If, for example, AGEN 1 is set to 48kS/s, and AGEN 2 is set to 44.1kS/s,
then the output of AGEN 2 will have about 44 nsecs of jitter on its edges.
Although this sounds a lot, it is high frequency noise shaped jitter that is easily
rejected by a receiving PLL, and is well within the requirements of the AES3
data eye spec.
AGEN 1 is also special in that it has a tone generator associated with it, so that
it can have an audio tone superimposed on it. The other AGENs cannot.
Can be
programmed for
Sample Rate (Fs)
Phase (Φ)
AES3 Message (M)
Signal from tone
generator (S)
Table 1 – AGENs, and what can be programmed
Manual for Software Version 2.0x
4
AGEN AES3 generators (AGEN 1–4). The
If other AGEN sample rates are set to integer
AGEN 1 AGEN 2
yes yes
yes yes
yes yes
yes No – digital
silence
Page 9
January 2001
(AES 2 -
AGEN 3 AGEN 4
yes yes
yes yes
yes yes
No – digital No – digital
silence silence
file 063992ma2a1.pdf available from website
email to: more@dcsltd.co.uk
web site: www.dcsltd.co.uk
AES 1
4)
If,