AM79C989JC datasheet(26/37 Pages) AMD

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Am79C989

PRELIMINARY

Control Register (Reg 18)

The Control Register (Reg 18) conﬁgures the port in

conjunction with the Auto-Negotiation registers. The

Control Register contains Read/Write (R/W) or Read/

Only (R/O) bits. This register is duplicated for each

port.

Table 18.

Control Register (Reg 18)

Bit(s)

Name

Description

Read/

Write

Default/

Reset

Force Link Good

Enable

1 = 10BASE-T link integrity state machine is forced to the “link

good” state;

0 = Normal operation resumes.

For internal test only (when link pulses are absent).

Not for general use in 10BASE-T applications.

R/W

14:6

Reserved

Written and read as zero.

R/O

Interrupt Enable

1 = For port 0, the Interrupt function through the QINT/CI- pin will

be active and the AUI port, if selected (bit 2 set), will operate in PCI

mode.

0 = For port 0, the interrupt function will not be available.

Ports 1, 2, and 3 are don’t cares.

Not effected by SRESET.

R/W

Disable

Link Pulse

Generation

1 = Link pulses sent from the 10BASE-T transmitter are

suppressed;

0 = Link Pulses not suppressed.

R/W

Auto Receive

Polarity Correction

Disable

1 = Polarity correction circuit at the front-end of the receive port

disabled (when the receive function is disabled, the receive port will

only accept frames with correct polarity);

0 = Self-correcting polarity circuit will be enabled at the receive

interface of the device.

R/W

AUI Select

Enable

1 = For port 0, Attachment Unit Interface is substituted for

10BASE-T port 0;

0 = Port 0 reverts to 10BASE-T function.

Ports 1, 2, and 3 are don’t cares. Not effected by SRESET.

R/W

Extended Distance

Enable

1 = 10BASE-T receive squelch thresholds reduced for reception of

frames farther than 100 meters.

0 = Squelch thresholds at standard 100 meter distance.

R/W

SQE_TEST

Disable

1 = SQE heartbeat, which occurs after each transmission, disabled;

0 = Heartbeat asserted on QCLSN approximately 1

µs after

transmission, for a duration of 1

µs;

When the port is conﬁgured for full duplex, heartbeat signal is

automatically disabled.

R/W

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