RS8234EBGC Mindspeed Technologies, RS8234EBGC Datasheet - Page 111

• Manufacturer Part Number: RS8234EBGC
• Description: RS8234EBGC ATM XBR SAR
• Manufacturer: Mindspeed Technologies

RS8234
ATM ServiceSAR Plus with xBR Traffic Management
Figure 5-5. Direct Index Lookup Method for AAL3/4
28234-DSH-001-B
5.2.2.4 AAL3/4 Lookup
Base Register (16)
RSM_TBASE
(RSM_ITB)
VPI [11:0]
VPI Index Table
VCI_IT_PNTR
VC_EN is a logic low, the cell is discarded and the CELL_DSC_CNT counter is
incremented. Optionally, the counter is not incremented if the AAL_TYPE field
has a value of ‘11’. VC_EN allows idle cells to be filtered if the PHY layer has
not already done so.
counter.
AAL3/4 MID multiplexing requires an additional level of indirection in channel
lookup for received AAL3/4 traffic. This is due to the fact that one Virtual
Connection can have a multiple number of connectionless messages (like SMDS
datagrams) multiplexed onto that one received connection. Each of these long
SDUs is identified by its MID value. Thus, the VCC lookup also includes the
MID value in the lookup mechanism.
described in the previous section. However, for AAL3/4 connections,
VCC_BLOCK_INDEX + VCI[5:0] points to an AAL3/4 Head RSM VCC Table
entry (see
points to the first entry of a block of AAL3/4 entries for one Virtual Connection,
with the MID value = 0.
received cell’s Virtual Connection and MID. The AAL3/4 lookup mechanism is
illustrated in
The reassembly coprocessor reads the first word of the VCC Table entry. If
If the channel is active, the RS8234 increments the CELL_RCVD_CNT
The VPI Index table and VCI Index table lookup is performed exactly as
That AAL3/4 Head entry contains the VCC_INDEX_BASE field which
VCC_INDEX_BASE + MID points to the RSM VCC table entry for the
Mindspeed Technologies
Table
VCI [15:x]
Figure
5-16).
5-5.
VCC_Block_Index
VCI Index Table
(for one VPI)
(RSM_VCCB)
RSM_TBASE
™
VCI [x-1:0]
(Mid=0)
5.2 Reassembly Functional Description
MID
5.0 Reassembly Coprocessor
VCC_INDEX_BASE
VCC Table Entries)
VCC Table entries
(Block of AAL3/4
Reassembly
(Block of 2 x
VCC Table
for 1 VC)
100074_026
5-7