T8207 Datasheet, PDF (28/158 Pages) Agere Systems – ATM Interconnect

CelXpres T8207
ATM Interconnect
Advance Data Sheet
September 2001
8 Look-Up Table (continued)
8.2 Organization
Organization is discussed in terms of 8-byte records. Differences in organization for 8-byte records and 16-byte
records will be discussed in Section 8.4, Extended Records. The look-up table may be configured to support up to
16 ports when multi-PHY mode is used, effectively creating a separate look-up table for each port.
For 32 ports, each even and odd pair of ports share a look-up table space.
All VPI, VCI, and OAM/RM records may be either 8 bytes or 16 bytes in length. (See Section 8.4, Extended
Records for information on 16-byte records.) Figure 4 shows the translation RAM memory map for 8-byte records
when the device is configured for 16 or less PHY ports. When greater than 16 PHY ports are used, the look-up
table is shared between even and odd ports. Figure 5 shows this translation RAM memory map. OAM/RM transla-
tion records are located at the bottom of the memory space with 64 OAM/RM records used by each port. If the
device is configured to support 16 to 32 ports, the first 1024 records will be used for OAM and RM translation
records. This translates to 8 Kbytes of memory for 8-byte records. The remaining memory is then used for VPI and
VCI records. For 8-byte records, when 16 ports or less are used, the base addresses of the OAM records are cal-
culated from the following equation:
OBA = PN × 8 × 64
In this equation, OBA is the OAM base address, PN is the port number, 8 is the number of bytes per record, and 64
is the number of records per port. For example, the OAM/RM translation records for port 2 will have a base address
of 1024 or 400h.
For 8-byte records, when greater than 16 ports are used, the base addresses of the OAM records are calculated
from the following equation:
OBA = INT(PN/2) × 8 × 64
In this equation, OBA is the OAM base address, PN is the port number; 8 is the number of bytes per record, and 64
is the number of records per port. The INT function specifies that the term within the parentheses is an integer, i.e.,
the fractional part is discarded. For example, the OAM/RM translation records for port 5 will have a base address of
1024 or 400h.
Note: If the device is configured to use less than 16 ports, the OAM/RM translation record memory space will be
allocated enough memory to handle ports 0 through the maximum port number used. For example, if the
device is configured to use ports 0, 2, 4, and 6 (see Section 9, UTOPIA Interface), the OAM/RM translation
record memory space will use 448 records (for ports 0 through 6). OAM/RM translation record memory
space for ports 1, 3, and 5 will be skipped even though the ports are not used.
Note: If the device is configured in PHY mode (see Section 9, UTOPIA Interface), the device supports only a single
PHY and the translation RAM memory will be addressed as port 0.
Separate VPI record base addresses may be set up for each port in multi-PHY mode (for up to 16 ports), and the
number of incoming VPI bits used as a pointer into the look-up table may be programmed. (See Section 14.3,
Extended Memory Registers, Table 103.) For 8-byte records, when 16 ports or less are used, the total memory
used by the VPI records is calculated using the following equation:
MS = NP x 2^NB x 8
In this equation, MS is the memory size used for VPI records, NP is the number of ports used, 8 is the number of
bytes per record, and NB is the number of incoming VPI bits used to address the look-up table.
For 8-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 8
In this equation, MS is the memory size used for VPI records, NP is the number of ports used (greater than 16),
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 discarded.
This calculated memory space must be reserved for VPI records.
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