AM79C984 datasheet(25/44 Pages) AMD

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P R E L I M I N A R Y

Am79C984A

Disable Automatic Receiver Polarity Reversal (Per TP

Port)

SI Data

0110 00##

SO Data

None

This command disables the Automatic Receiver Polarity

Reversal function for the TP port designated by the two

least-signiﬁcant bits in the command byte. If this func-

tion is disabled on a TP port receiving with reversed

polarity (due to a wiring error), the TP port will fail the

Link Test due to the incorrect polarity of the received

Link pulses.

The state of Automatic Polarity Reversal function is set

by SI on reset. If SI is HIGH at the rising edge of RST,

the eIMR device disables Automatic Polarity Reversal.

If SI is LOW at the rising edge of RST, the eIMR device

enables Automatic Polarity Reversal.

Enable Automatic Receiver Polarity Reversal (Per TP

Port)

SI Data

0111 00##

SO Data

None

This command enables the Automatic Receiver Polarity

Reversal function for the TP port designated by the two

least-signiﬁcant bits in the command byte. If enabled in

a TP port, the eIMR chip will automatically invert the

polarity of that port’s receiver circuitry if the TP port is

detected as having reversed polarity (due to wiring er-

ror). After reversing the receiver polarity, the TP port

could then receive subsequent (reverse polarity)

packets correctly.

Disable Receiver Extended Distance Mode (Per TP

Port)

SI Data

0110 10##

SO Data

None

This command disables the Receiver Extended

Distance Mode and restores the RXD circuit of the trans-

ceiver to normal squelch levels for the TP port driver

designated by the two least-signiﬁcant bits of the com-

mand data.

Enable Receiver Extended Distance Mode (Per TP Port)

SI Data

0111 10##

SO Data

None

This command modiﬁes the RXD circuit of the trans-

ceiver for the TP port driver designated by the two least-

signiﬁcant bits of the command data. The RXD squelch-

threshold value is lowered to accommodate signal at-

tenuation associated with lines longer than 100 meters.

At reset, Receiver Extended Distance Mode is disabled

and the RXD circuit defaults to normal squelch-thresh-

old values.

Disable Software Override of LEDs

(Per Port - AUI and TP, Global)

SI Data

1001 ####

SO Data

None

This command disables Software Override of the Port

LEDs.

Individual LEDs and combinations of LEDs can be

selected via the lower four bits of the command byte as

follows:

####

Port(s) affected

0000-0011 TP0 - TP3

0100-0111 Reserved

1000

AUI port

1001

Reserved

1010

Reserved

1011

All TP ports

1100

All ports

1101

Global

1110

Reserved

1111

Reserved

Following command execution, the attributes displayed

on the LEDs will be determined by LDC0-2. Software

Override of LEDs is disabled after reset.

Enable Software Override of Bank A LEDs (Per Port -

AUI and TP, Global)

SI Data

1011 ####

SO Data

None

This command forces the LEDs in Bank A to blink. In-

dividual LEDs and combinations of LEDs can be select-

ed via the lower four bits of the command byte as follows:

####

Port(s) affected

0000-0011 TP0 - TP3

0100-0111 Reserved

1000

AUI port

1001

Reserved

1010

Reserved

1011

All TP ports

1100

All ports

1101

Global

1110

Reserved

1111

Reserved

The designated LED driver(s) will switch between LOW

and ‘off’ at the rate set by the Software Override Blink

Rate command. Enable Software Override of Bank A

LEDs references the blink rate last issued and overrides

any other attribute speciﬁed by LDC0-2. Software Over-

ride of LEDs is disabled after reset.

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