Released
PMC-Sierra, Inc.
PM9311/2/3/5 ETT1™ CHIP SET
Data Sheet
PMC-2000164
ISSUE 3
ENHANCED TT1™ SWITCH FABRIC
Table 2. TDM Reservation Table (Continued)
Meaning
Field
Size (bits)
Subport
2
Identifies the source subport (if in subport mode, else 0)
1 if the output side TDM entry is valid
Output
VLD
1
5
4
Input Port
Input port that the output expects to receive from
Output
vector
A four-bit vector which defines the fanout of the subports that should receive
a TDM cell.
The EPP contains two TDM tables so that one table can be used by the fabric while the system software is
configuring the other table. All EPPs must use the same table at the same time. A TDM LCS Control
Packet is used to specify which of the two tables is being used at any given time.
At the start of the Frame, a TDM pointer in each port begins at entry 0 in the table and advances one entry
every cell time. During every cell time, if the “current” TDM table Send entry is valid, the EPP checks to see
if the cell at the head of the appropriate TDM queue has a TDM flow ID (tag) that matches the entry in the
table. If not, then nothing special is done. If they do match then the EPP informs the Scheduler that it will
be sending a TDM cell at some fixed time in the future. This prevents the Scheduler from trying to schedule
a best-effort cell from that port at the same time. Figure 27 shows the logic at the ingress port.
56
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
PMC [ PMC-SIERRA, INC ]
