PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 190

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

Semiconductor Group
4.7.2.2
Single-channel loop-backs are always performed directly in the IEC-Q. No difference
between the B1-channel and the B2-channel loop-back control procedure exists. They
are therefore discussed together.
In EOC Auto mode the B1-channel is closed with the EOC-command LB1. LB2 causes
the channel B2 to be looped back. Because these functions are latched, both channels
may be looped back simultaneously by sending first the command to close one channel
followed by the command for the second one.
In the EOC Transparent mode, single channels are closed with the corresponding
MON-8-commands.
Single-channel loop-backs are resolved in the same manner as described for the
complete loop-back. The NT may be deactivated with layer 2 while single loop-backs are
closed.
4.7.2.3
Loop-back #1A is always closed in the repeater. Functionally it corresponds to
loop-backs #1 and #3 on the exchange and on the network side. If a line contains more
than one repeater unit, it is possible to address each unit individually in order to close
loop-back #1A in the specified unit only.
For loop-back #1A everything described in section "Analog Loop-Back (No. 1/No. 3)",
page 187 applies: The loop-back is opened with the C/I-command RES, closed with the
C/I-command ARL, and it is closed as near to the U-interface as possible. The difference
results from the fact that the command ARL needs to be generated by the repeater
control unit (µP or ASIC) according to national repeater specifications.
This specification defines an EOC-command which will activate loop-back #1A if
received in conjunction with the repeater address (001
transparent mode. The repeater control unit watches for MON-0-commands with
address (001
control unit sends the C/I-code ARL to the LT-RP and loop-back #1A will be closed.
For more information, see "EOC Addressing Management", page 257.
Figure 82 illustrates this in a system with two repeater units where the second unit is
requested to close loop-back #1A.
Single-Channel Loop-Backs
Repeater Loop-Back (No. 1A)
B
). If the predefined loop-back #1A command is received, the repeater
190
B
). The NT-RP is operating in
Operational Description
Data Sheet 01.99
PEB 2091
PEF 2091