VT6516 datasheet(46/73 Pages) ETC

46 / 73 page

VIA Technologies, Inc.

Preliminary VT6516 Datarsheet

-46-

07H

SDRAM Command Drive Strength Configure

bit0: RDCSDV --- SDRAM Chip Select Drive Strength

bit1: RMADV --- SDRAM MA drive strength

(including RAS,CAS,WE,MA,BA)

bit2: RMDDV --- SDRAM MD drive strength

SDRAM_DR_

CFG

[2:0]

R/W

08H

SDRAM Bank Interleaving Disable

0: enable interleaving (default)

1: disable interleaving

BK_IL_DIS

[0]

R/W

4.2 Registers of SRAM Control Module

* Base Address: 0800H

Addres

(offset

)

Function

Name

Bits

Defau

Value

00H

SRAM Read Command Interleave Disable

0: enable interleaving (default)

1: disable interleaving

SRAM_READ

_IL_DIS

[0]

R/W

4.3 Registers of Queue Control Module

* Base Address: 0C00H

Addres

(offset

)

Function

Name

Bits

Defau

Value

00-

02H

Free Memory Flow Control Threshold register

As FREEMCNT(a register in buffer control) < FMFCT, the

congestion control function will be triggered to command the TMAC

module of the source port, destined to a congested port, to send out

a flow control frame for full duplex mode, or to make back-pressure

for half duplex mode. See the context about congestion control for

details.

Larger the threshold value more sensitive the congestion control

mechanism, i.e. maybe poor utilization for packet buffers but larger

packet loss rate. Smaller the threshold value less sensitive the

congestion control mechanism, i.e. maybe good utilization for

packet buffers but smaller packet loss rate. It depends on the

network configuration and traffic pattern. The recommended

threshold value is 256.

FMFCT

[18:0

]

03H

Cut Through Enable

0: Disable Cut Through (default)

1: Enable Cut Through

Note: REMEMBER to enable the cut-through function to improve

the switching latency. For 100Mbps input port, the smallest latency

for cut-through is 288 bytes time (288x8x10 ns). For 10Mbps input

port, the smallest latency for cut-through is 96 bytes time (96x8x100

ns).

CUT_THROU

GH_EN

[0]

R/W

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