TXC-05802AIPQ Transwitch Corporation, TXC-05802AIPQ Datasheet - Page 21

• Manufacturer Part Number: TXC-05802AIPQ
• Manufacturer: Transwitch Corporation

Specifications of TXC-05802AIPQ

• Operating Supply Voltage (typ): 3.3/5V
• Operating Temperature Classification: Industrial
• Package Type: PQFP
• Mounting: Surface Mount
• Pin Count: 208
• Lead Free Status / Rohs Status: Not Compliant

Figure 16 shows a starting condition for the split-queue mode some time after congestion conditions a) and b)
have both become present, with three cells in the CBR cell queue when CBRLIMIT = 3 and two cells in the
VBR cell queue when VBRLIMIT = 2 (i.e., both queues are at the congestion level).
As before, cells #1, #2 and #3 left the queues before the congestion occurred and are not marked for conges-
tion indication (PT = X0X). When the outlet link becomes free and the cells in the Sync FIFO shift to the left,
cells flow in to the Sync FIFO from the four data cell queues in priority order. Since the VBR queue contains
two cells when VBRLIMIT = 2, congestion continues to exist while all cells in the CBR cell queue are moved
into the Sync FIFO, so cells #4, #5 and #6 are marked with congestion indications (PT = X1X). Now, assuming
no more cells are joining the queues, the CBR cell queue is empty but the VBR cell queue is still at the
VBRLIMIT value with two cells, so cell #7 is also marked with a congestion indication. But when it moves to the
Sync FIFO only one cell is left in the VBR cell queue, so conditions a) and b) no longer both exist, and this cell
#8 is not marked with a congestion indication (PT = X0X).
Outlet
Port
Cell
Note: The IFECN control bit is set to 1. The EFCI congestion indication is the middle bit of the PT sequence
(X0X or X1X). Its value is determined when the cell leaves the queue.
Figure 16. Example of Congestion Indication in Split-Queue Mode (QM=1)
CBR
X0X
Cell
#1
Sync FIFO
VBR
X0X
Cell
#2
ABR
X0X
Cell
#3
- 21 -
CBR
VBR
X1X
X1X
Cell
Cell
#4
#7
VBRLIMIT = 2
CBR
VBR
X1X
X0X
Cell
Cell
#5
#8
Control Data Cell Queue (Priority 1)
CBRLIMIT = 3
CBR
X1X
Cell
#6
CBR Cell Queue (Priority 2)
VBR Cell Queue (Priority 3)
ABR Cell Queue (Priority 4)
Ed. 3, November 1999
TXC-05802
CUBIT- Pro
TXC-05802-MB