
134
Am79C965A
CSR15: Mode Register
Bit
Name
Description
This register
’
s fields are loaded
during the PCnet-32 controller
initialization routine with the
corresponding Initialization Block
values or a direct I/O write has been
performed to this register.
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15
PROM
Promiscuous Mode.
When PROM =
“
1
”
, all incoming
receive frames are accepted.
Read/write accessible only when
STOP bit is set.
14
DRCVBC Disable Receive Broadcast. When
set, disables the PCnet-32 controller
from receiving broadcast messages.
Used for protocols that do not
support broadcast addressing,
except as a function of multicast.
DRCVBC is cleared by H_RESET or
S_RESET (broadcast messages will
be received) and is unaffected by
STOP.
Read/write accessible only when
STOP bit is set.
13
DRCVPA Disable Receive Physical Address.
When set, the physical address
detection (Station or node ID) of the
PCnet-32 controller will be disabled.
Frames addressed to the nodes
individual physical address will not
be recognized (although the frame
may be accepted by the EADI
mechanism).
Read/write accessible only when
STOP bit is set.
12
DLNKTST Disable
Link
Status.
When
DLNKTST =
“
1
”
, monitoring of Link
Pulses is disabled. When DLNKTST
=
“
0
”
, monitoring of Link Pulses is
enabled. This bit only has meaning
when the 10BASE-T network
interface is selected.
Read/write accessible only when
STOP bit is set.
11
DAPC
Disable Automatic Polarity Cor-
rection. When DAPC =
“
1
”
, the
10BASE-T receive polarity reversal
algorithm is disabled. Likewise,
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 reduced by
4.5 dB below the standard
10BASE-T value (approximately
3/5) and the unsquelch 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 threshold.
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
”
differential to
operate transformer coupled loads
(Ethernet 2 and 802.3). When TSEL
= 1, the DO+ idles at a higher value
with respect to DO-, yielding a
logical HIGH state (Ethernet 1).
This bit only has meaning when the
AUI network interface is selected.