参数资料
型号: GT-48002A
厂商: Galileo Technology Services, LLC
英文描述: Switched Fast Ethernet Controller for 100BaseX(100BaseX交换式快速以太网控制器)
中文描述: 交换式快速以太网控制器(100BaseX交换式快速以太网控制器的100BaseX)
文件页数: 17/102页
文件大小: 1001K
代理商: GT-48002A
Switched Fast Ethernet Controller
Revision 1.2
21
Table 3: GT-48002A DRAM Address Mapping
5.1
Rx Buffer Threshold Programming
The number of receive buffers allocated to each port of the GT-48002A is controlled by the RxBufThr field in the Rx
Buffer Threshold register and the DisBufThr* pin. The default value is 80 buffers per port for 1MB DRAM and 140 buff-
ers per port for 2MB DRAM. If the buffer threshold is disabled (by clearing the BufThrEn bit in the Global Control regis-
ter or if the DisBufThr* pin is held LOW) the GT-48002A dynamically allocates the buffers to the 2 ethernet ports and
the PCI bus port. In other words, there are no limits on each buffers’ allocation. The Rx Buffer Threshold value can be
used to tune performance during development. See Table 4 for Rx Buffer Threshold settings. If a received packet over-
flows the Rx buffer allowance, then that packet will be discarded and the Dropped Packets counter will be incremented.
The overflow of the Rx buffer threshold is also indicated by the “Receive Buffer Full” LED in the Serial and Parallel LED
Interfaces (Rx Buffer Threshold must be enabled).
Table 4: Setting the Rx Buffer Threshold
Mem o ry
D esc ri pti o n
1Mbyt e
2Mbyt e
Rx Buffers
320 Buffers for 1Mbyte
1008 Buffers for 2 Mbyte
0x00000 - 0x7cfff
0x00000 - 0x17cfff
PCI Tx Descriptor
0x7d000 - 0x08efff
0x17d000 - 0x18efff
PCI Rx Descriptor
0x8f000 - 0x9afff
0x18f000 - 0x19afff
Reserved
4KBytes
0x9b000 - 0x09bfff
0x19b000 - 0x19bfff
Tx Descriptor
0x09c000 - 0x09ffff
0x19c000 - 0x19ffff
Address Table
0xa0000 - 0xfffff
0x1a0000 - 0x1fffff
D i sB uf Thr * P i n
Bu fT h r En Bi t
Re s u lt
HIGH
1
Receive Buffer Size is limited to the
value of RxBufThr
HIGH
0
Dynamic Receive Buffer Allocation
LOW
1
Dynamic Receive Buffer Allocation
LOW
0
Dynamic Receive Buffer Allocation
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