T8207 Datasheet, PDF (40/158 Pages) Agere Systems – ATM Interconnect

CelXpres T8207
ATM Interconnect
Advance Data Sheet
September 2001
8 Look-Up Table (continued)
To calculate the 16-byte translation record address for the F4 type OAM cell, the incoming VCI is multiplied by 16,
and the resulting product is added to the port’s OAM base address. For the special case when the incoming VCI is
six and the PTI in the cell header is “110,” the OAM translation record address is the sum of the port’s OAM base
address and 200h.
The 16-byte OAM type F5 translation record offset is determined from the incoming cell’s PTI using the following
table. The OAM translation record address is the sum of this offset and the port’s OAM base address.
Table 15. F5 Translation Record Addresses Table—Extended Mode
PTI
“100”
“101”
“110”
“111”
OAM Translation Offset
Port’s OAM base address plus 210h
Port’s OAM base address plus 220h
Port’s OAM base address plus 230h
Port’s OAM base address plus 240h
In extended mode, the memory space used by the VPI records also changes. The total memory now used by the
VPI records is calculated using the following equation for 16 or less ports:
MS = NP x 2^NB x 16
In this equation, MS is the memory size used for VPI records, NP is the number of ports used, 16 is the number of
bytes per record, and NB is the number of incoming VPI bits used to address the look-up table.
For 16-byte records, when greater than 16 ports are used, the total memory used by the VPI records is calculated
using the following equation:
MS = INT(NP/2) x 2^NB x 16
In this equation, MS is the memory size used for VPI records, NP is the number of ports used (for greater than
16 ports), 8 is the number of bytes per record, and NB is the number of incoming VPI bits used to address the look-
up table. The INT function specifies that the term within the parentheses is an integer, i.e., the fractional part is dis-
carded.
To address the 16-byte VPI translation record, the selected incoming VPI bits (see Section 8.3, Look-Up Proce-
dure) are concatenated and multiplied by 16 to create an offset into the look-up table. The sum of this offset and
the VPI base address creates the actual VPI translation record address associated with the incoming cell. Note
that only bits 3 through 18 of the VPI base address are stored in the LUT X configuration structure.
To address the 16-byte VCI translation record, the VCI from the cell’s header is multiplied by 16 and added to bits 3
through 18 of the VCI offset which is obtained from the VPI record. This sum is the final offset into the look-up table.
This final offset should then be added to the translation RAM memory beginning address 100000h (Table 125) to
obtain the final address.
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