VIA Technologies, Inc.
Preliminary VT6508 Datasheet
-41-
02H
Backoff configuration
bit 0: CAP mode
à DEC’ s capture effect
(default: CAP=0)
bit 1: MBA mode
à HP’ s capture effect
(default: MBA=0)
bit 2: EEFAST mode
à drop the 2
nd collided
packet for testing purpose, accelerate the drop
event
(default: EEFAST=0)
bit 3: CRANDOM mode
à use another random
algorithm
(default: CRANDOM=0)
bit 4: OFSET
à parameter for backoff timer,
For OFSET=1, the TMAC will follow the 802.3
standard backoff algorithm. For OFSET=0, the
TMAC will select the backoff time for the 1
st and
2
nd collision as that of the 3rd collision, i.e. the
possible the backoff time for the 1
st and 2nd
collision is ranged from 0 to 7 in unit of slot time.
(default: OFSET=1)
For the number of excessive retries, please see
the strapping pin SD[52:51].
BOFFCFG
[4:0]
5’ b1000
0
R/W
03H
MAC media type configuration
bit 0: SPD_10M
à value 0: 100Mbps,
value 1: 10Mbps
bit 1: HALF_DPX
à 1: half duplex, 0: full duplex
bit 2: RCV_FC_DIS
à
1: disable receive flow control frame
0: enable receive flow control frame
bit 3: XMT_FC_DIS
à
1: disable send flow control frame for
full-duplex mode
0: enable send flow control frame
Note: this is configured automatically by auto-
polling control or CPU if auto-polling is
disabled to that port. There is no forced
mode if auto-polling is enabled to that port.
MACCFG
[3:0]
0
R/W
04H
IO port enable
bit 0: input port enable
0: input disabled, (drop incoming packets)
1: input enabled
bit 1: output port enable
0: output disabled (default)
1: output enabled
bit 2: output port dequeue hold
1: dequeue disabled
0: dequeue enabled (default)
Note that the broadcast domain is determined by
the CPUIO_CFG[1] and 9 bits of all Ethernet
ports’ IO_CFG[1]. If IO_CFG[1]==0, this
Ethernet port must be not within the broadcast
domain.
IO_CFG
[2:0]
0
R/W
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