SMSC LAN9312 manual 420

High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface

Datasheet

14.5.4.10Buffer 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		TYPE	DEFAULT
31:5	RESERVED				RO	-
4	Random Discard Weight Table RnW				R/W	0b
	Specifies a read (1) or a write (0) command.
3:0	Random Discard Weight Table Index				R/W	0h
	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.
		BIT	BUFFER USAGE LEVEL
		VALUES
		0000		0 to 7
		0001		8 to 15
		0010		16 to 23
		0011		24 to 31
		0100		32 to 39
		0101		40 to 47
		0110		48 to 55
		0111		56 to 63
		1000		64 to 79
		1001		80 to 95
		1010		96 to 111
		1011		112 to 127
		1100		128 to 159
		1101		160 to 191
		1110		192 to 223
		1111		224 to 255

Revision 1.4 (08-19-08)	420	SMSC LAN9312
	DATASHEET