psf21911 ETC-unknow, psf21911 Datasheet - Page 47

• Manufacturer Part Number: psf21911
• Description: Isdn Echocancellation Circuit Terminal Applications Iec-q
• Manufacturer: ETC-unknow

Testing Block Error Counters
Figure 18 illustrates how the IEC-Q TE supports testing of the LT’s block error counters.
Transmission errors are simulated with artificially corrupted CRCs. With two commands
the cyclic redundancy checksum can be inverted in the downstream and in the upstream
direction. A third command offers to invert single FEBE-bits.
With EOC command NCC the LT notifies the NT of corrupted CRCs. Again, there are
differences in the functional behavior of the NEBE-counter depending on the EOC mode:
With EOC command RCC the LT requests the NT-side to send corrupted CRCs. In EOC
auto mode the IEC-Q TE will react automatically with a permanently inverted upstream
CRC. In EOC transparent mode this reaction has to be prompted by a MON-8 CCRC
command. Note that MON-8 CCRC is not excecuted if it was not preceeded by the EOC
command RCC.
There are also differences in the functional behavior of the FEBE-counter depending on
the EOC mode:
The EOC command RTN disables all previously sent EOC commands. In EOC
transparent mode EOC command RTN must be followed by a MON-8 NORM command
to become effective.
With the MON-8-command SFB it is possible to invert single FEBE-bits. Because this
command does not provoke permanent FEBE-bit inversion but sets only one FEBE-bit
to (0) per SFB command, it is possible to predict the exact FEBE-counter reading.
Semiconductor Group
Auto-mode
Transparent mode
EOC
Transparent mode
Auto mode
NEBE-detection stopped, no MON-1 NEBE-messages
and NEBE-counter disabled
NEBE-detection enabled, MON-1-message NEBE issued
and NEBE-counter enabled
FEBE-detection stopped, no MON-1 FEBE-messages
and FEBE-counter disabled
FEBE-detection enabled, MON-1-message FEBE issued
and FEBE-counter en
47
abled
U-Transceiver
PSB 21911
PSF 21911
11.97