PM7324 Datasheet, PDF (431/473 Pages) PMC-Sierra, Inc – SATURN User Network Interface ATM Layer Solution

S/UNI-ATLAS
DATASHEET
PMC-1971154
ISSUE 7
11.4.1.2Adding a Connection
PM7324 S/UNI-ATLAS
S/UNI-ATM LAYER SOLUTION
The following are the microcontroller actions required to provision a connection:
1. Determine the next available VC Table address. Initialize the contents of the VC Table Record
via the Microprocessor RAM Address and Data registers (0x190 through 0x1CB). Care
should be taken to set the following fields appropriately:
All counts should be set to zero.
The "Status" and “Internal Status” fields should be set to all zero’s.
The "Active" bit of the "Configuration" field should be set to one.
2. Perform a binary search to determine the insertion point. The last pointer accessed in the
search shall be the one modified, be it a Primary Search Table entry, left branch or right
branch.
3. Find a free Secondary Search Table entry and initialize it. The only exception to this is when a
single VC Table Record exists in a tree, in which case the solitary Secondary Search Table
entry is modified.
The value of the "Select" is set to the index of the most significant bit which differs between the
new VC and the "nearest" existing VC, which was found in step 2. A few insights need
highlighting:
1. If there is an overlap between Primary and Secondary Search keys (eg. the Primary key is the
VPI), the intersecting bits are excluded from the binary search based on the fact they will
always be the same in both keys.
2. Due to fact that the Primary Search key includes the PHY identification, NNI and UNI
connections will never reside in the same binary tree. Therefore, the "Select" determination
algorithm needs to start its bit comparison at the correct bit (the first bit of the ATM header for
NNI and the fifth bit of the ATM header for UNI) to ensure a valid search tree.
3. Perform a SRAM write (via the Microprocessor RAM Address and Data registers) to
incorporate the new Secondary Search Table entry in the existing tree structure. This step
must be performed last to ensure a binary search in progress is not corrupted.
Five distinct types of insertions are possible based on the existing tree structure:
1. The binary tree is empty. In this case, the null primary search table pointer is modified to point
to a newly created Secondary Search Table entry. Because no bits within the Secondary
Search Key are required, both the left and right branches of the Secondary Search Table entry
point to the same VC Table Record. The "select" field should be set to zero.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC AND FOR ITS CUSTOMERS’ INTERNAL USE 423