GTS/DEC/006
6
Gain control bandwidth
This setting controls how quickly the automatic gain control responds to a change in amplitude; a higher setting (up to 100%)
results in a slower filter response while a smaller setting (say 20%) results in a faster response.
Offset control bandwidth
This setting controls how quickly the automatic offset control responds to a change in offset; a higher setting (up to 100%)
results in a slower filter response while a smaller setting (say 20%) results in a faster response.
Loop bandwidth filter
It is desirable to restrict loop bandwidth at higher bit rates. This is to prevent the PLL frequency from moving too far away from
the PCM clock frequency and thereby introducing jitter.
Choosing fill words
Care must be taken when choosing fill words. For example, 0xAAAA (101010…..) or 0x5555 (010101…..) can result in loss of
sync because 0xAAAA at 20Mb/s looks like 0xAAAA at 10Mb/s when using NRZ-M or NRZ-S. A fill word of, for example,
0x7E7E results in no loss of sync. By the same token, a fill word of 0xCCCC (11001100….) results in the same problem when
using 20mb/s NRZ-L. Therefore, try to avoid repetitions of these types when choosing fill words.
Loopback tester
The GTS/DEC/006 features a loopback tester, which transmits a PCM frame to allow system checks. The loopback tester
transmits frames as configured in the XidML setup. The loopback tester allows for dynamic and fixed data to be transmitted. The
first eight parameters transmitted are dynamic counters that rollover to zero. The rest of the parameters are a fixed word (which
is 0x1234). At present, the loopback tester only generates the minor frame layout as given in the configuration.
N
OTE
:
The GTS/DEC/006 driver software is a minor frame decoder. Client software can use the SDK functions to decommutate
major frames by adding minor frame tracking logic.
Status LEDs
The GTS/DEC/006 uses LEDs as shown in the following figure to indicate the current status of the card.
N
OTE
:
The state of LEDs is undefined between power-on and the first driver access to the PCI card. Once the card is config-
ured, behavior is as shown in the following table until the PC is powered off.
Figure 2: PCI card LEDs
TABLE 11
Status LED description
LED
NAME
DESCRIPTION
1
IRIG-B
Lights when the IRIG time signal is successfully received.
2
BS(0)
Lights solid green when the bit synchronizer is in lock with an incoming data stream on channel 0.
3
DECOM(0)
Lights solid green when the decommutator is in a lock state; when not lit the decommutator is in a loss,
verify or check state.
4
BS(2)
Lights solid green when the bit synchronizer is in lock with an incoming data stream on channel 2.
5
BS(1)
Lights solid green when the bit synchronizer is in lock with an incoming data stream on channel 1.
1
2
3
4
5
6
