
PEF 82902
Functional Description
Data Sheet
65
2001-11-09
2.4.4.1
Monitoring of Code Violations
The running digital sum monitor (RDSM) computes the running digital sum from the
received ternary symbols by adding the polarity of the received user data (+ 1, 0,
–
1). At
the end of each block, the running digital sum is supposed to reflect the number of the
next column in
Table 15
.
A code violation has occurred if the running digital sum is less than one or more than four
at the end of a ternary block, or if the ternary block 0 0 0 (three user symbols with zero
polarity) is found in the received data.
If at the end of a ternary block no error was found, the running digital sum retains its
current value. If the counter value is greater than 4, it is set to 4 at the beginning of the
next ternary block, if its value is 0 or less, it is set to one. So after a code violation has
been detected, the RDSM synchronizes itself within a period depending on the received
data pattern. Note there are some transmission errors which do not cause a code
violation.
2.4.4.2
Block Error Counter (RDS Error Counter)
The T-SMINT I provides a block error counter. This feature allows monitoring the
transmission quality on the U-interface.
On the NT side a block error is given, if a U-frame with at least one code violation has
been detected (near-end block error). In the following frame the NT transmits a positive
M-symbol upstream.
On the LT side a block error is given, if a U-frame with at least one code violation has
been detected (near-end block error) or a positive M-symbol has been received from the
NT (far-end block error).
The current status of the block error counter can be retrieved by the system interface.
When the block error counter is read (register RDS), it is automatically reset. The counter
is enabled in all states listed in
Table 17
and reset in all other states. The counter is
saturated at its maximum value (255).
0 + 0,
0 +
–
+ + 0,
–
0
–
1
1
1
1
1
1
0
1
1
1
0
1
0 0
–
Table 17
Active States
SBC Sychronizing
Wait for INFO U4H
Transparent
Table 16
4B3T Decoding Table