AMD
P R E L I M I N A R Y
132
Am79C965
wise, when DAPC = “0”, the
polarity reversal algorithm is
enabled.
This bit only has meaning when
the 10BASE-T network interface
is selected.
Read/write accessible only when
STOP bit is set.
10
MENDECL
MENDEC Loopback Mode. See
the description of the LOOP bit in
CSR15.
Read/write accessible only when
STOP bit is set.
9
LRT/TSEL
Low Receive Threshold (T-MAU
Mode only)
Transmit
Mode
Select
(AUI
Mode only)
LRT
Low Receive Threshold. When
LRT = “1”, the internal twisted
pair receive thresholds are re-
duced by 4.5 dB below the stan-
dard
10BASE-T
value
(approximately 3/5) and the un-
squelch threshold for the RXD
circuit will be 180–312 mV peak.
When LRT = “0”, the unsquelch
threshold for the RXD circuit will
be
the
standard
10BASE-T
value, 300 - 520 mV peak.
In either case, the RXD circuit
post squelch threshold will be
one half of the unsquelch thresh-
old.
This bit only has meaning when
the 10BASE-T network interface
is selected.
Read/write accessible only when
STOP bit is set. Cleared by
H_RESET or S_RESET and is
unaffected by STOP.
TSEL
TSEL Transmit Mode Select.
TSEL controls the levels at which
the AUI drivers rest when the AUI
transmit port is idle. When TSEL
= 0, DO+ and DO- yield “zero” dif-
ferential to operate transformer
coupled loads (Ethernet 2 and
802.3). When TSEL = 1, the DO+
idles at a higher value with re-
spect to DO-, yielding a logical
HIGH state (Ethernet 1).
This bit only has meaning when
the AUI network interface is se-
lected.
Read/write accessible only when
STOP bit is set. Cleared by
H_RESET or S_RESET and is
unaffected by STOP.
8-7 PORTSEL[1:0]
Port Select bits allow for software
controlled selection of the net-
work medium.
PORTSEL settings of AUI and
10BASE-T are ignored when the
ASEL bit of BCR2 (bit 1) has
been set to ONE.
The network port configuration is
shown in Table 41.
Table 41. Network Port Configuration
ASEL
Link Status
Network
PORTSEL[1:0] (BCR2[1])
(of 10BASE-T)
Port
0X
1
Fail
AUI
0X
1
Pass
10BASE-T
0 0
0
X
AUI
0 1
0
X
10BASE-T
1 0
X
GPSI
1 1
X
Reserved
Refer to the section on General
Purpose Serial Interface for de-
tailed information on accessing
GPSI.
Read/write accessible only when
STOP bit is set. Cleared by
H_RESET or S_RESET and is
unaffected by STOP.
6
INTL
Internal Loopback. See the de-
scription of LOOP, CSR15-2.
Read/write accessible only when
STOP bit is set.
5
DRTY
Disable Retry. When DRTY = “1”,
PCnet-32 controller will attempt
only one transmission. If DRTY =
“0”, PCnet-32 controller will at-
tempt 16 retry attempts before
signaling a retry error. DRTY is
defined when the initialization
block is read.
Read/write accessible only when
STOP bit is set.
4
FCOLL
Force Collision. This bit allows
the collision logic to be tested.
PCnet-32 controller must be in
internal loopback for FCOLL to
be valid. If FCOLL = “1”, a colli-
sion will be forced during loop-
back transmission attempts. a
Retry Error will ultimately result.
If FCOLL = “0”, the Force Colli-
sion logic will be disabled.
Read/write accessible only when
STOP bit is set.
3
DXMTFCS
Disable Transmit CRC (FCS).
When
DXMTFCS
=
0,
the