78Q2120C データシートの表示（PDF） - Teridian Semiconductor Corporation

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78Q2120C

10/100BASE-TX Transceiver

Teridian Semiconductor Corporation 

78Q2120C

10/100BASE-TX

Transceiver

MR0: Control Register (continued)

BIT

0.8

0.7

0.6:0

SYMBOL

DUPLEX

COLT

RSVD

TYPE

R/W

R/W

R

DEFAULT

(1)

0

0

DESCRIPTION

Duplex Mode: This bit determines whether the device supports full-

duplex or half-duplex. A ‘1’ indicates full-duplex operation and a ‘0’

indicates half-duplex. This bit will default to ‘0’ upon reset and will

be writeable if the TECH[2:0] pins are all logic zero and auto-

negotiation is not enabled. If auto-negotiation is not enabled and

the TECH[2:0] pins are set to indicate that only full-duplex is

supported, this bit will be forced to ‘1’ and will not be writeable. If

auto-negotiation is not enabled and the TECH[2:0] pins are set to

indicate that only half-duplex is supported, this bit will be forced to

‘0’ and will not be writeable. When auto-negotiation is enabled, this

bit will not be writeable and will have no effect on the device. If the

TECH[2:0] pins are brought to zero from another value, this bit will

retain its original value until it is overwritten.

Collision Test: When this bit is set to ‘1’, the device will assert the

COL signal in response to the assertion of the TX_EN signal.

Collision test is disabled if the PCSBP pin is high. Collision test can

be activated regardless of the duplex mode of operation.

Reserved

MR1: Status Register

Bits 1.15 through 1.11 reflect the ability of the 78Q2120C as configured by the TECH[2:0] pins. They do not

reflect any ability changes made via the MII Management interface to bits 0.13 (SPEEDSL) , 0.12 (ANEGEN) and

0.8 (DUPLEX).

BIT SYMBOL TYPE DEFAULT DESCRIPTION

1.15

100T4

R

0

100BASE-T4 Ability: Reads ‘0’ to indicate the 78Q2120C does not

support 100Base-T4 mode.

1.14 100X_F R

(1)

100BASE-TX Full Duplex Ability:

0 : Not able

1 : Able

1.13 100X_H R

(1)

100BASE-TX Half Duplex Ability:

0 : Not able

1 : Able

1.12 10T_F

R

(1)

10BASE-T Full Duplex Ability:

0 : Not able

1 : Able

1.11 10T_H

R

(1)

10BASE-T Half Duplex Ability:

0 : Not able

1 : Able

1.10 100T2_F R

0

100BASE-T2 Full Duplex Ability: Reads ‘0’ to indicate the

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

Page: 12 of 35

© 2009 Teridian Semiconductor Corporation

Rev 1.3

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