AM79C983A Advanced Micro Devices, AM79C983A Datasheet - Page 38

• Manufacturer Part Number: AM79C983A
• Description: Integrated Multiport Repeater 2 (IMR2)
• Manufacturer: Advanced Micro Devices

Byte 0
Byte 1
are ignored. This feature is useful when implementing
port switching. The IMR2 device connected to the QuIET
device serial interface will still report correct status on
the Link and Polarity LEDs. The ports default to the
XENA value on reset.
Pn/AUI/RAUI 0
Note: If a port is isolated during an incoming or transmit-
ted packet, repeating the packet is immediately stopped.
If a port is connected during an incoming packet, the ac-
tual connection is delayed until after the end of the packet.
If a port is connected while the IMR2 device is repeating
a packet, the connection is made immediately.
Extended Distance Enable
Address:
Setting a bit on this register lowers the input threshold
on RXD of the corresponding QuIET transceiver. This
allows the use of a twisted pair cable longer than 100
meters. This register is only in effect if the correspond-
ing port is connected to a QuIET device. On reset, this
register defaults to Extended Distance Option disabled.
TPn/SPn
Automatic Last Source Address Intrusion Control
Address:
Automatic Intrusion Control disables a port automati-
cally when a valid packet (no errors) is received with a
source address which is not a valid address for that
port. Before a bit on this register is set, the correspond-
ing Last Source Address Register should contain a
valid address for that port. On reset, this register de-
faults to Automatic Intrusion Control with Last Source
Address disabled. See note under Automatic Preferred
Source Address Intrusion Control .
38
Byte 0
Byte 1
Byte 0
Byte 1
TP7
SP3 SP2 SP1 SP0
MSB
D Port Read/Write
D Port Read/Write
D Port Read/Write
MSB
P7
0
P7
0
MSB
1110 1000
1110 1001
TP6
P6
0
P6
0
1
1
0 Extended
TP5 TP4 TP3 TP2 TP1 TP0
P5
RAUI
P5
RAUI
Isolate the corresponding port
Connect the corresponding port
Extended
disabled
enabled
P4
AUI P11 P10 P9
P4
AUI P11 P10 P9
TP11 TP
P3
P3
Distance
Distance
P2
P2
10
TP9 TP8
P R E L I M I N A R Y
P1
P1
Option
Option
LSB
P0
P8
P0
P8
LSB
LSB
Am79C983A
Automatic Preferred Source Address Intrusion Control
Address:
Automatic Intrusion Control disables a port automatically
when a valid packet (no errors) is received with a source
address which is not a valid address for that port. Before
a bit on this register is set, the corresponding Preferred
Address register should contain a valid address for that
port. On reset, this register defaults to Automatic Intrusion
Control with Preferred Source Address disabled.
Pn/AUI/RAUI
Note: The Automatic Preferred Source Address Intru-
sion Control Register and the Automatic Last Source Ad-
dress Intrusion Control Register work together. If intrusion
on a port is not enabled on either register, intrusion control
is not performed for that port. If intrusion on a port is en-
abled on only one of the intrusion control registers, intru-
sion control is based on the corresponding enabled
register. If intrusion on a port is enabled on both intrusion
control registers, the port is disabled if the source address
fails to match both the Last Source Address Register and
the Preferred Source Address Register.
Last Source Address Lock Control
Address:
Whenever the source address of an incoming packet is
different from the Last Source Address Register, the
new source address is written into the Last Source Ad-
dress Register. Setting a bit on this register disables
automatic updating of the Last Source Address Regis-
ter based on the last received packet. The Last Source
Address Register can still be written into via the node
processor interface. On reset, this register defaults to
Last Source Address Lock disabled. Note that a re-
peater that uses Last Source Address Lock Control will
not comply with IETF RFC 1516.
Pn/AUI/RAU
Byte 0
Byte 1
Byte 0
Byte 1
MSB
D Port Read/ Write
MSB
D Port Read/Write
P7
0
P7
0
1110 1010
1110 1011
P6
0
P6
EP
0
1
1
0
Automatic Intrusion Control with
Last Source Address enabled
Automatic Intrusion Control with
Preferred
enabled
P5
RAUI
Automatic Intrusion Control with
P5
RAUI
Preferred
disabled
Automatic Intrusion Control with
Last Source Address disabled
P4
AUI P11 P10 P9
P4
AUI P11 P10 P9
P3
P3
Source
Source
P2
P2
P1
P1
Address
Address
P0
P8
P0
P8
LSB
LSB