Datasheet

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78Q2120C

10/100BASE-TX

Transceiver

MR1: Status Register

BIT SYMBOL TYPE DEFAULT DESCRIPTION

1.9 100T2_H R 0 100BASE-T2 Half Duplex Ability: Reads ‘0’ to indicate the

78Q2120C does not support 100Base-T2 full duplex mode.

1.8 EXTS R 0 Extended Status Information Availability: Reads ‘0’ to indicate the

78Q2120C does not support Extended Status information on MR15.

1.7 RSVD R 0 Reserved

1.6 MFPS R 0 Management Frame Preamble Suppression Support: A “0”

indicates that the 78Q2120C can read management frames with a

preamble.

1.5 ANEGC R 0 Auto-Negotiation Complete: A logic one indicates that the Auto-

Negotiation process has been completed, and that the contents of

registers MR4,5,6 are valid.

1.4 RFAULT RC 0 Remote Fault: A logic one indicates that a remote fault condition

has been detected and remains set until it is cleared. This bit can

only be cleared by reading this register (MR1) via the management

interface.

1.3 ANEGA R (1) Auto-Negotiation Ability: When set, this bit indicates the device’s

ability to perform Auto-Negotiation. The value of this bit is

determined by the ANEGEN bit (MR0.12).

1.2 LINK R 0 Link Status: A logic one indicates that a valid link has been

established. If the link status should transition from an OK status to

a NOT-OK status, this bit will become cleared and remains cleared

until it is read.

1.1 JAB RC 0 Jabber Detect: In 10Base-T mode, this bit is set during a jabber

event. After a jabber event, the bit remains set until cleared by a

read operation.

1.0 EXTD R 1 Extended Capability: Reads ’1’ to indicate the 78Q2120C provides

an extended register set (MR2 and beyond).

MR2: PHY Identifier Register 1

BIT SYMBOL TYPE VALUE DESCRIPTION

2.15:0 OUI

[23:6]

R 000Eh

Organizationally Unique Identifier: This value is 00-C0-39 for

TERIDIAN Semiconductor Corporation. This register contains the

first 16-bits of the identifier.

MR3: PHY Identifier Register 2

BIT SYMBOL TYPE VALUE DESCRIPTION

3.15:10 OUI

[5:0]

R 1Ch

Organizationally Unique Identifier: Remaining 6 bits of the OUI.

3.9:4 MN R 0Ch

Model Number: The last 2 digits of the model number 78Q2120C are

encoded into the 6 bits.

3.3:0 RN R 9h

Revision Number: The value ‘1001’ corresponds to the ninth revision

of the silicon.