AM79C985JC datasheet(28/48 Pages) AMD

28 / 48 page

Am79C985

PRELIMINARY

Enable Automatic Receiver Polarity Reversal (Per TP

Port)

SI Data

0111 0###

SO Data (Pri)

None

SO Data (Sec)

None

This command enables the Automatic Receiver Polarity

Reversal function for the TP port designated by the three

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. Designated port values of b111 through b100

in the command byte correspond to TP7 through TP4 in

the primary eIMR+ device. Designated port values of

b011 through b000 in the command byte correspond to

TP3 through TP0 in the secondary eIMR+ device.

Disable Receiver Extended Distance Mode (Per TP

Port)

SI Data

0110 1###

SO Data (Pri)

None

SO Data (Sec)

None

This command disables the Receiver Extended Dis-

tance Mode and restores the RXD circuit of the trans-

ceiver to normal squelch levels for the TP-port driver

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

mand data. Designated port values of b111 through

b100 in the command byte correspond to TP7 through

TP4 in the primary eIMR+ device. Designated port val-

ues of b011 through b000 in the command byte corre-

spond to TP3 through TP0 in the secondary eIMR+

device.

Enable Receiver Extended Distance Mode (Per TP

Port)

SI Data

0111 1###

SO Data (Pri)

None

SO Data (Sec)

None

This command modiﬁes the RXD circuit of the trans-

ceiver for the TP-port driver designated by the three

least-signiﬁcant bits of the command data. The RXD

squelch-threshold value is lowered to accommodate

signal attenuation associated with lines longer than 100

meters. Designated port values of b111 through b100

in the command byte correspond to TP7 through TP4

in the primary eIMR+ device. Designated port values of

b011 through b000 in the command byte correspond to

TP3 through TP0 in the secondary eIMR+ device. 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 (Pri)

None

SO Data (Sec)

None

This command Disables software override of the Port

LEDs.

Individual LEDs and combinations of LEDs can be se-

lected via the lower four bits of the command byte, as

follows:

####

Port(s) affected

0000-0111 TP0 - TP7

1000

Primary AUI

1001

Secondary AUI

1010

Both AUI ports

1011

All TP ports

1100

All ports

1101

Primary Global

1110

Secondary Global

1111

All Global

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 (Pri)

None

SO Data (Sec)

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

0000-0111 TP0 - TP7

1000

Primary AUI

1001

Secondary AUI

1010

Both AUI ports

1011

All TP ports

1100

All ports

1101

Primary Global

1110

Secondary Global

1111

All Global

The designated LED drivers(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. Soft-

ware override of LEDs is disabled after reset.

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