PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 112

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

Semiconductor Group
MON-0-commands may be passed at any instant and need to be transferred only once
(applicable for Auto and Transparent mode). Code repetition is performed within the chip
by the EOC processor.
A summery of the EOC procedure in EOC Auto and Transparent modes is given in
Figure 50, page 114. If the microprocessor mode is used, the IOM
50 can be replaced by the µP interface.
EOC Access in LT-
In LT-Auto mode the "return message" reception is enabled after an EOC-command has
been transmitted downstream. The activation of this function causes the LT IEC-Q to
watch the EOC of the U-interface and to issue a MON-0-message after an identical
EOC-message has been received during three consecutive frames. Thus in LT-Auto
mode an acknowledgment of the MON-0-command is even possible if the new message
is not different from the previous one.
If no MON-0-command has been transmitted downstream, a MON-0-message is issued
only after the "triple-last-look" criterion is fulfilled and if this message is different from the
one previously accepted. New messages will be passed upstream independently of the
address used, i.e. not only messages addressed with (000) or (111) but all received
EOC-messages will be transmitted with MON-0-messages.
LT-Transparent Mode
In LT-transparent mode every 6 ms a MON-0-message containing the last received
EOC-message is issued. This occurs even if no change occurred in the EOC-channel.
No "triple-last-look" is performed before a MON-0-message is sent.
NT-EOC-Auto Mode
The seven defined EOC-commands listed in Table 19 will be executed automatically by
the IEC-Q if they were sent with the address (000) or (111) and the d/m bit was set to
message (1). Every new EOC-command will be acknowledged immediately, i.e. no
triple-last-look (e.g. acknowledgment of LB1 command reads 01
acknowledgment is transmitted.
Table 19
Code
Hex.
00
50
51
52
Symbol
LBBD
Predefined EOC Messages
LB1
LB2
H
Auto Mode
Function
Hold
Close complete loop
Close loop B1
Close loop B2
112
Operational Description
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-2 interface in Figure
H
, 51
Data Sheet 01.99
H
) before the
PEB 2091
PEF 2091