参数资料
型号: ZL50418/GKC
厂商: ZARLINK SEMICONDUCTOR INC
元件分类: 网络接口
英文描述: DATACOM, LAN SWITCHING CIRCUIT, PBGA553
封装: 37.50 X 37.50 MM, 2.33 MM HEIGHT, MS-034, HSBGA-553
文件页数: 100/155页
文件大小: 1928K
代理商: ZL50418/GKC
ZL50418
Data Sheet
49
Zarlink Semiconductor Inc.
Bank A. This means that a 7-byte segment of Bank A bandwidth is idle, and furthermore, the next 8-byte segment
of Bank B bandwidth is idle, because the first 8 bytes of the next frame will be written to Bank A, not B. This
scenario results in a maximum 15 bytes of waste per frame, which is always acceptable because the interframe gap
is 20 bytes.
The CPU management port gets treated like any other port, reading and writing to alternating memory banks
starting with Bank A. The VLAN Index Mapping Table and Mac Address Table are duplicated in Bank A and B.
When the CPU writes an entry to the VLAN Index Mapping Table it has to write the same data in bank A and bank
B. Search engine data is written to both banks in parallel. In this way, a search engine read operation can be
performed by either bank at any time without a problem.
5.2
Memory Requirements
To speed up searching and decrease memory latency, the external MAC address database is duplicated in both
memory banks. To support 64 K MAC address, 2 MB/bank memory is required. When VLAN support is enabled,
512 entries of the MAC address table are used for storing the VLAN ID in the VLAN Index Mapping Table.
Up to 2 K Ethernet frame buffers are supported and they will use 3 MB of memory. Each frame uses 1536 bytes.
The maximum system memory requirement is 4 MB. If less memory is desired, the configuration can scale down.
Figure 9 - Memory Configuration
Bank A
Bank B
Tagged-based VLAN
Max. Frame Buffers
Max MAC Address
1 M
Disable
1 K
32 K
1 M
Enable
1 K
31.5 K
2 M
Disable
2 K
64
2 M
Enable
2 K
63.5 K
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