VT6508 datasheet(35/48 Pages) ETC1

35 / 48 page

VIA Technologies, Inc.

Preliminary VT6508 Datasheet

-35-

1E-1FH Destination Ports Bit Mask for Port 8 (CPU port)

0: no affection on port 8’ s incoming packets

that will be forwarded with lookup

not 0: port 8’ s next incoming packets will be

forwarded by CPU_PM, rather than lookup.

CPU_PM will be set as ‘ 0’ after processing

exact ONE port 8’ s incoming packet.

Note that this function can facilitate the

implement of some special system features, e.g.

production testing utility, boot diagnosis utility.

CPU_PM

[8:0]

R/W

20H

Reserved Special Internal Control

bit 0 – enable early cpu port broadcast filtering

bit 3:1 – unused

bit 4 – DROP_CONGESTION_WHEN_STARV

bit 6:5 – SWITCH_MAC_MATCH_MODE

bit 7 – LOOPUP_OPTION

Note that only the bit 0 is used for normal

operation setting. Except the bit 0 is used for the

normal operation setting, the other bits are used

only in Verilog simulation.

SPECIAL_CTL

[7:0]

R/W

21H

CPU port related forwarding configuration

bit 0 – enable forwarding broadcast packets with

DMAC=0xffffffffffff to CPU

(default = 0 : disable)

bit 1 – enable forwarding spanning-tree packets

to CPU

(default = 0 : disable)

bit 2 – enable forwarding unicast packets with

DMAC = switch MAC base to CPU

(default = 0 : disable)

bit 3 – enable forwarding multicast packets with

DMAC = 01-80-C2-00-00-02~0F to CPU

(default = 0 : disable forwarding to CPU

port, i.e. drop these packets)

Note that the USER_PM in VT3061 is changed as

10-bit signal from 10 output port enabling bits.

The three register bits are used to enable/disable

forwarding the above three types of frames to the

CPU port.

If CPU_FWD_CFG[1]=1, i.e. forwarding

spanning-tree packets to CPU is disabled, these

SPT packets will be broadcasted, just like the

case for Ethernet Hub.

CPU_FWD_CFG

[2 3:0]

R/W

22-23H

Drop On

Value 1: the corresponding port’ s drop feature is

enabled. Any incoming packets destining to any

one port in congestion will be dropped by

Forwarding Control by setting port mask = 0.

Value 0: the port’ s drop feature is disabled.

This signal is from TMAC.

DROP_ON

[8:0]

R/O

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