LAN9313 Datasheet, PDF (366/398 Pages) SMSC Corporation – Three Port 10/100 Managed Ethernet Switch with MII

13.3.4.10
Three Port 10/100 Managed Ethernet Switch with MII
Datasheet
Buffer Manager Random Discard Table Command Register (BM_RNDM_DSCRD_TBL_CMD)
Register #:
1C09h
Size:
32 bits
This register is used to read and write the Random Discard Weight table. A write to this address
performs the specified access. This table is used to set the packet drop probability verses the buffer
usage.
For a read access, the Buffer Manager Random Discard Table Read Data Register
(BM_RNDM_DSCRD_TBL_RDATA) can be read following a write to this register.
For a write access, the Buffer Manager Random Discard Table Write Data Register
(BM_RNDM_DSCRD_TBL_WDATA) should be written before writing this register.
BITS
DESCRIPTION
31:5 RESERVED
4 Random Discard Weight Table RnW
Specifies a read (1) or a write (0) command.
3:0 Random Discard Weight Table Index
Specifies the buffer usage range that is accessed.
There are a total of 16 probability entries. Each entry corresponds to a range
of the number of buffers used by the ingress port. The ranges are structured
to give more resolution towards the lower buffer usage end.
TYPE
RO
R/W
R/W
BIT
VALUES
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
BUFFER USAGE LEVEL
0 to 7
8 to 15
16 to 23
24 to 31
32 to 39
40 to 47
48 to 55
56 to 63
64 to 79
80 to 95
96 to 111
112 to 127
128 to 159
160 to 191
192 to 223
224 to 255
DEFAULT
-
0b
0h
Revision 1.2 (04-08-08)
366
DATASHEET
SMSC LAN9313/LAN9313i