am79c981 Advanced Micro Devices, am79c981 Datasheet - Page 17

• Manufacturer Part Number: am79c981
• Description: Integrated Multiport Repeater Plus? Imr+? ??9
• Manufacturer: Advanced Micro Devices

AUI Port Enable
This command enables a previously disabled AUI port.
Note that a partitioned AUI port may be reconnected by
first disabling (AUI Port Disable Command) and then re-
enabling the port with this command.
All ports are enabled upon reset.
TP Port Disable
The TP port designated in the command byte will be dis-
abled upon receiving this command. Subsequently, the
IMR+ device will ignore all inputs appearing at the dis-
abled port’s receive pins and will not transmit any data or
JAM Sequence on that port’s transmit pins. Issuing this
command will also cause a TP port to have its partition-
ing state machine returned to its Idle State (Port Recon-
nected). Therefore, a partitioned port may be
reconnected by first disabling and then re-enabling the
port. The disabled port will continue to report correct
Link Test Status.
TP Port Enable
This command enables a previously disabled TP port.
Re-enabling a disabled port causes the port to be placed
into Link Test Fail state. This ensures that packet frag-
ments received on the port are not repeated to the rest of
the network. Note that to force a TP port into the Link Fail
state and/or to reconnect a partitioned TP port, the port
should first be disabled (TP Port Disable Command)
and then re-enabled with this command. All ports are
enabled upon reset.
Disable Link Test Function of a TP Port
This command disables the Link Test Function at the TP
port designated in the command byte, i.e., the TP port
will no longer be disconnected due to Link Fail. A TP port
which has its Link Test Function disabled will continue to
transmit Link Test Pulses. If a twisted pair port has Link
Test disabled, then reading the Link Test Status indi-
cates it being in Link Test Pass.
SI data:
SO data:
SI data:
SO data:
(### is TP port number)
SI data:
SO data:
(### is TP port number)
SI data:
SO data:
(### is TP port number)
00111111
None
00100###
None
00110###
None
01000###
None
PRELIMINARY
Am79C981
Enable Link Test Function of a TP Port
This command re-enables the Link Test Function in the
TP port designated in the command byte. This com-
mand executes only if the designated TP port has had
the Link Test Function disabled by the Disable Link Test
Function command. Otherwise, the command is ig-
nored. Link Test is enabled upon reset.
Disable Automatic Receiver Polarity Reversal
This command disables the Automatic Receiver Polarity
Reversal Function for the TP port designated in the
command byte. If this function is disabled on a TP port
with reverse polarity (due to a wiring error), then the TP
port will fail Link Test due to the reversed polarity of the
Link Pulses. If the Link Test Function is also disabled on
the TP port, then the received reversed polarity packets
would be repeated to all other network ports in the IMR+
chip as inverted data. Automatic Polarity reversal is dis-
abled upon reset.
Enable Automatic Receiver Polarity Reversal
This command enables the Automatic Receiver Polarity
Reversal Function for the TP port designated in the
command byte. If enabled in a TP port, the IMR+ chip
will automatically invert the polarity of that TP port’s re-
ceiver circuitry if the TP port is detected as having
reversed polarity (due to a wiring error). After reversing
the receiver polarity, the TP port could then receive sub-
sequent (reverse polarity) packets correctly.
GET (Read) Opcodes
AUI Port Status
The combined AUI status allows a single instruction to
be used for monitoring AUI port. The four status bits re-
ported are:
SI data:
SO data:
(### is TP port number)
SI data:
SO data:
(### is TP port number)
SI data:
SO data:
(### is TP port number)
SI data:
SO data:
01010###
None
01100###
None
01110###
None
10001111
PBSL0000
AMD
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