
196
Am79C978
TBR17: 10BASE-T PHY Control/Status Register
(Register 17)
This register is used to control the configuration of the
10 Mbps PHY unit of the Am79C978 home networking
device. See Table 75.
Table 75.
TBR17: 10BASE-T PHY Control/Status Register (Register 17)
Note:
1. For these loopback paths, the data is also transmitted out of the MDI pins (TX±).
Bits
Name
Description
Read/Write
H/W
Reset
Soft Reset
15
Reserved
R/W
0
Retains
Previous
Value
14
Reserved
R/W
0
Retains
Previous
Value
13
Force Link Good
Enable
1 = link status forced to link up state
0 = link status is determined by the device
R/W
0
0
12
Disable Link Pulse
1 = Link pulses sent from the
10BASE-T transmitter are suppressed
R/W
0
0
11
SQE_TEST Disable
1 = Disables the SQE heartbeat which occurs
after each 10BASE-T transmission
0 = The heart beat assertion occurs on the
COL pin approximately 1 μs after transmission
and for a duration of 1 μs.
R/W
0
0
10
Reserved
R/W
0
0
9
Jabber Detect Disable
1 = disable jabber detect
0 = enable jabber detect
R/W
0
0
8:7
Reserved
R/W
00
00
6
Receive Polarity
Reversed
1 = Receive polarity of the 10BASE-T receiver
is reversed
0 = Receive polarity is correct
RO
0
0
5
Auto Receive Polarity
Correction Disable
1 = polarity correction circuit is disabled for
10BASE-T
0 = Self correcting polarity circuit is enabled
R/W
0
0
4
Extended Distance
Enable
1 = 10BASE-T receive squelch thresholds are
reduced to allow reception of frames which are
greater than 100 meters
0 = Squelch thresholds are set for standard
distance of 100 meters
R/W
0
0
3
TX_DISABLE
1 = TX± outputs not active for 10BASE-T. TX±
outputs to logical
“
0
”
for PECL.
0 = Transmit valid data
R/W
0
0
2
TX_CRS_EN
1 = CRS is asserted when transmit or receive
medium is active
0 = CRS is asserted when receive medium is
active
RO
0
0
1
Reserved
RO
0
0
0
PHY Isolated
1 = Internal PHY is isolated
0 = Internal PHY is enabled
RO
0/1
0/1