GTS/DEC/003
5
Getting the most of the GTS/DEC/003
N
OTE
:
The GTS/DEC/003 is a half-length PCI-form board and is not currently verified for use in a PCI-X slot. Voltage levels are
3.3 or 5 volts. Dimensions are: W = 0.6 inches (15.24 mm) x D = 6.9 inches (175.26 mm) × H = 4.2 inches (106.68 mm).
GTS Software Development Kit (SDK)
The GTS SDK 3 includes APIs for system definition, programming and real-time data access, and documentation with detailed
examples.
The GTS SDK 3 provides developers and system integrators with a toolkit for generating XidML® metadata files and
programming the card. It also offers real-time access to decommutated data with time tags and status registers.
Bit synchronizer performance tuning
If offset modulation is affecting performance, adjust the offset bandwidth from 100% downwards to compensate. Likewise, if
amplitude modulation is affecting performance, decrease the gain bandwidth.
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/003 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
TABLE 8
Decommutator settings
SETTING
CHOICE
DEFAULT
Input polarity
True
False
True
Auto invert polarity
True
False
False
Sync word mask
0 to 64
Based on size of sync word
Sync word error tolerance
0 to 16, but less than 25% of sync word bits
0
PCM clock phase [°]
0° / 90° / 180° / 270°
0°
