PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 180

• Manufacturer Part Number: PEF2091
• Description: ICs for Communications(ISDN Echocancellation Circuit)
• Manufacturer: Siemens Semiconductor Group

PEB 2091
PEF 2091
Operational Description
4.5.1.3
Testing Block Error Counters
The block error counter is tested by simulating transmission errors on the line. To
simulate transmission errors artificially corrupted CRC bits (as a matter of fact, inverted
CRC bits) are send from the LT to the NT side and vice versa. The device detecting
corrupted CRC bits will start incrementing the corresponding block error counter which
can in turn be read out by a MON-8 command, as described above in this chapter. Figure
78, page 183, gives a complete overview of the test procedures. Describing the
commands needed to perform these tests and the corresponding device behavior is the
scope of this section.
MON-8 CCRC causes the IEC-Q to permanently transmit inverted CRCs. This command
may be used on LT side with the LT in Transparent or Auto mode. On the terminal side
CCRC is only required when the device is operated in transparent mode.
In NT-Auto Activation mode corrupted CRCs can be requested directly by the LT side
with the EOC command RCC. Again the CRC will be permanently inverted.
With the MON-8 command SFB it is possible on LT and NT side 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. For more information about MON-8 codes, refer to "MON-8
Codes", page 228.
Note 51: The main application for setting single FEBE-bits are repeater stations not
operating in the LT-RP- or NT-RP mode).
Request Corrupt CRCs (RCC)
If the EOC Auto mode is used on the NT side (see "EOC Auto/Transparent Mode", page
55) this command requests the NT side to transmit corrupted (i.e. inverted) CRCs
upstream to test the LT NEBE-counter. Simultaneously the FEBE-counter and
MON-1-messages of the NT are disabled.
If the EOC Transparent mode is used on the NT side the CRC will not be corrupted, the
FEBE-counter is enabled and MON-1 FEBE-messages will be issued, i.e. the IEC-Q will
not react to this command.
This command is a predefined EOC command which can be controlled by the MON-0
message issued on the LT side downstream (see "Access to EOC of U-Interface", page
110).
Semiconductor Group
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Data Sheet 01.99