AM79C981 datasheet(17/40 Pages) AMD

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PRELIMINARY

1–87

Am79C981

AUI Port Enable

SI data:

00111111

SO data:

None

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

SI data:

00100###

SO data:

None

(### is TP port number)

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,

partitioned

port

may

reconnected by first disabling and then re-enabling the

port. The disabled port will continue to report correct

Link Test Status.

TP Port Enable

SI data:

00110###

SO data:

None

(### is TP port number)

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

SI data:

01000###

SO data:

None

(### is TP port number)

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.

Enable Link Test Function of a TP Port

SI data:

01010###

SO data:

None

(### is TP port number)

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

SI data:

01100###

SO data:

None

(### is TP port number)

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

SI data:

01110###

SO data:

None

(### is TP port number)

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

SI data:

10001111

SO data:

PBSL0000

The combined AUI status allows a single instruction to

be used for monitoring AUI port. The four status bits re-

ported are:

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