User guide

86 RealCT Direct API Developer Guide
Chapter 3: T1 Networking
SIGNALING_BIT_ERROR
A signaling bit error occurs when a bit pattern that does not
belong in the protocol was present on the line. The invalid bit
pattern must be present for longer than the debouncing and
deglitching timings in order to generate this error.
If you receive a signaling bit error, compare the bit pattern in
RTNI_lineStatus.RawPattern to the ones expected by the
protocol to be sure your application and the CO are using the
same protocol. Call the carrier for more information about their
protocol, or use AccuSpan to get more information about the
signaling.
If you frequently get a signaling bit error that isn’t related to
any particular event, you might have a problem with the
connection. In this case the application should monitor the
status of the carrier. If the number of bipolar violations and
buffers slips is high, the line quality is poor. Check the gain your
CSU is set to provide, the length of cable, and the equalization
parameters set on the hardware.
RawPattern ‘RawPattern’ contains the received and transmitted signaling
bits. The upper byte contains the received pattern while the
lower byte contains the transmitted pattern. Each of these bytes
contains only four significant bits. These bits contain the value
for signaling bits A, B, C, and D. Bit A is the most significant bit,
while bit D is the least significant bit.
For example, if ‘RawPattern’ contains 0x0F05, then the receive
pattern is 0x0F and the transmit pattern is 0x05.
Receive= 0x0F=1111, and A=B=C=D=1
Transmit= 0x05=0101, and A=C=0 and B=D=1
Only ESF framing uses all four signaling bits. If your
application uses D3/D4 framing, bits C and D are undefined. For
example, if ‘RawPattern’ contains 0x0F05 and you are using
D3/D4 framing, then
Receive= 0x0F=1111, and A=B=1
Transmit= 0x05=0101, and A=0 and B=1
and you ignore bits C and D.
Follow the same conventions when using AccuSpan in signaling
mode. In D3/D4 framing, bits C and D are not used. If you want
to transmit a pattern AB=10, transmit ABCD=10XX =0x08,
0x09, 0x0A, or 0x0B.