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266 Software Developer’s Manual
Register Descriptions
Auto MDIX Parallel
Detect Bypass
4
Auto_MDIX Parallel Detect Bypass.
Bypasses the fix to IEEE auto-MDIX
algorithm for the case where the PHY is
in forced-speed mode and the link
partner is auto-negotiating.
1b = Strict 802.3 Auto-MDIX algorithm.
0b = Auto-MDIX algorithm handles
Auto-Negotiation disabled modes. This
is accomplished by lengthening the
auto-MDIX switch timer before
attempting to swap pairs on the first time
out.
R/W 0b 0b
PRE_EN 5
Preamble Enable
0b = Set RX_DV high coincident with
SFD.
1b = Set RX_DV high and RXD =
preamble (after CRS is asserted).
R/W 1b 1b
Reserved 6 Write to 0b for normal operation. R/W 0b 0b
Smart Speed 7
1b = Smart Speed selection enabled.
0b = Smart Speed selection disabled.
R/W 0b 0b
1
TP Loopback
(10BASE-T)
8
1b = Disable TP loopback during half-
duplex operation.
0b = Normal operation.
R/W 1b 1b
Reserved 9 Write to 0b for normal operation. R/W 0b 0b
Jabber (10BASE-T) 10
1b = Disable jabber.
0b = Enable jabber.
R/W 0b 0b
Bypass 4B5B
(100BASE-TX)
11
1b = Bypass4B5B encoder and
decoder.
0b = Normal operation.
R/W 0b 0b
Bypass Scramble
(100BASE-TX)
12
1b = Bypass scrambler and
descrambler.
0b = Normal operation.
R/W 0b 0b
Transmit Disable 13
1b = Disable twisted-pair transmitter.
0b = Normal operation.
R/W 0b 0b
Link Disable 14
1b = Force link pass
0b = Normal operation
For 10BASE-T, this bit forces the link
signals to be active. In 100BASE-T
mode, setting this bit should force the
Link Monitor into it’s LINKGOOD state.
For Gigabit operation, this merely
bypasses Auto-Negotiation—the link
signals still correctly indicate the
appropriate status.
R/W 0b 0b
Reserved 16:15
Always read as 0b. Write 0b for normal
operation.
R/W 0b 0b
1. The default for this bit is determined by EEPROM bit SSPEED.
Table 13-32. PHY Port Configuration Register Bit Description
Field Bit(s) Description Mode HW Rst SW Rst