PEB 20550
PEF 20550
Functional Description
Semiconductor Group
87
01.96
2.2.8.3 Control Channel Delay
Depending on the selected system configuration different delays between the activation
of the control channel and the corresponding D-channel response occur.
Table 14
Control Channel Delay Examples
Beware of Arbiter Locking!
In the state "limited selection", the D-channel arbiter sends the "blocked" information to
the terminal from which the last HDLC-frame was received. Since the "blocked"
information reaches the terminal with several IOM-frames delay
t
CCDD
(e.g. after
5
×
125
μ
s) the terminal may already have started sending a second HDLC-frame. On
reception of the "blocked" information the terminal immediately aborts this frame.
Since the abort sequence of the second frame reaches the ELIC with several frames
delay
t
DCDU
, the full selection counter value must be set so that the D-channel arbiter re-
enters the state "full selection" only after the abort sequence of the second frame has
reached the ELIC.
If the D-channel arbiter re-enters the "full selection" state (in which it again sends an
"available" information to the terminal) before the abort sequence has reached the ELIC,
it would mistake a ’0’ of the second frame as the start of a new frame. When the delayed
abort sequence arrives at the ELIC, the D-channel arbiter would then switch back to the
state "limited selection" and re-block the terminal. Thus the D-channel arbiter would
toggle between sending "available" and "blocked" information to the terminal, forever
aborting the terminal‘s frame. The arbiter would have locked.
Number of Frames (= 125
μ
s)
Blocked
→
Available
min.
4
System
Configuration
Circuit Chain
Available
→
Blocked
min.
4
max.
8
max.
8
U
PN
line card -
- U
PN
phone
U
PN
line card -
- S
0
adapter -
- S
0
phone
U
PN
line card -
- U
PN
adapter -
- U
PN
phone
ELIC + OCTAT-P
+ ISAC-P TE
ELIC + OCTAT-P
+ ISAC-P TE +
SBCX + ISAC-S
ELIC + OCTAT-P
+ ISAC-P TE +
ISAC-P TE +
ISAC-P TE
ELIC + QUAT-S
+ ISAC-S TE
9
13
5
9
9
13
9
13
S
0
line card
- S
0
phone
4
8
4
8