PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 146

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

Semiconductor Group
– Leave for state "Awake" after NT wake up tone (TN) was detected and the C/I-code
– Leave for state "Alerting" after C/I-commands "AR", "ARX", "AR0" or "UAR" and not
– Leave for state "Reset for Loop" after C/I-command "ARL" was received
Combinations of transition criteria are possible. Logical "AND" is indicated by "&" (TN &
DC), logical "OR" is written "or" and for a negation "/" is used. The start of a timer is
indicated with "TxS" ("x" being equivalent to the timer number). Timers are always
started when entering the new state. The action resulting after a timer has expired is
indicated by the path labelled "TxE".
The sections following the state diagram contain detailed information about all states and
signals used. These details are mode dependent and may differ for identically named
signals/states. They are therefore listed for each mode.
Cold and Warm Starts
Two types of start-up procedures are supported by the IEC-Q: cold starts and warm
starts.
Cold starts are performed after a reset and require all echo and equalizer coefficients to
be recalculated. This procedure typically is completed after 1-7 seconds depending on
the line characteristics. Cold starts are recommended for activations where the line
characteristics have changed considerably since the last deactivation.
A warm start procedure uses the coefficient set saved during the last deactivation. It is
therefore completed much faster (maximum 300 ms). Warm starts are however
restricted to activations where the line characteristics do not change significantly
between two activations.
Regarding the path in the transition diagram, cold starts have in particular that the IEC-Q
has entered the state ’Test’ (e.g. due to a reset) prior to an activation. The activation
procedure itself is then identical in both cases. Therefore, the following sections apply to
both warm and cold starts.
4.4.2
This section is applicable for the following LT modes:
– LT mode
– COT 512 mode
– COT 1536 mode
DC is present in the downstream direction
TN were received
State Machine in LT Modes
(512 kHz – 4096 kHz)
(512 kHz)
(1536 kHz)
146
Operational Description
Data Sheet 01.99
PEB 2091
PEF 2091