W6692 Datasheet, PDF (30/104 Pages) Winbond – PCI Bus ISDN S/T-Controller

Preliminary Data Sheet
W6692 PCI ISDN S/T-Controller
7.2.4 D Channel Access Control
The D channel access control includes collision detection and priority management. The collision detection is always enabled.
The priority management procedure as specified in ITU-T I.430 is fully implemented in W6692.
A collision is detected if the transmitted D bit and the received echo bit do not match. When this occurs, D channel
transmission is immediately stopped and the echo channel is monitored to attempt the next D channel access. The layer 1 module
uses an internal signal to inform layer 2 module of the collision condition (DRDY bit goes inactive in D_XSTA register).
There are two priority classes: class 1 and class 2. Within each class, there are normal and lower priority levels.
TABLE 7.4 D PRIORITY CLASSES
Priority class
1
Priority class
2
Normal level
8
10
Lower level
9
11
The selection of priority class is via the AR8/AR10 command. The following table summarizes the commands/indications used
for setting the priority classes:
TABLE 7.5 D PRIORITY COMMANDS/INDICATIONS
Command
Symbol
Activate request, set priority 8
AR8
Activate request, set priority 10 AR10
Indication
Abbr.
Activate indication with priority 8 AI8
Activate indication with priority 10 AI10
Code
1000
1001
1100
1101
Remarks
Activation command, set D channel priority to 8
Activation command, set D channel priority to 10
Remarks
Info 4 received, D channel priority is 8 or 9
Info 4 received, D channel priority is 10 or 11
7.2.5 Frame Alignment
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Publication Release Date: Sep 30, 1999
Revision 0.9