ML6680

9

Modes of Operation

Four configurations are possible with the ML6680,

as follows:

1.Standard Media Converter: Senses ISO/IEC8802-5

phantom power and generates ISO/IEC8802-5

fiberoptic insertion or bypass requests.

2.Concentrator Media Converter: Recognizes the ISO/

IEC8802-5 fiberoptic insertion or bypass requests and

drives the ISO/IEC8802-5 phantom circuits.

3.Lobe or Ring Out Port Media Converter: Recognizes

the ISO/IEC8802-5 fiberoptic insertion or bypass

requests.

4.Ring In Port Media Converter: Generates ISO/

IEC8802-5 fiberoptic insertion or bypass requests.

Modifies the internal signal paths depending on the

presence or absence of a fiberoptic link, and on the

reception of the ISO/IEC8802-5 “Insertion Key Echo.”

CONFIGURATION 1

Standard Media Converter:

This configuration is selected by tying KEYGEN to VCC.

There are always two fixed signal paths, one from TPINP and

TPINN to OPVCC and OPOUT, and another from OPINP

and OPINN to TPOUTP and TPOUTN. The generation of

the “Insertion Key” or “Bypass Key” is exclusively controlled

by the logic values at PHTM1 and PHTM2. The “Insertion

Key” is generated when both PHTM1 and PHTM2 go low,

and stay low for at least 26.5ms. If the “Insertion Key Echo”

is received within the following 100ms, the part goes to

the “Insert State” and the LED output INSERTED goes low.

During the generation of the “Insertion Key,” and while

waiting for the “Insertion Key Echo” the states of PHTM1

and PHTM2 do not have any effect. When the part is in

the “Insert State” and either PHTM1 or PHTM2 goes high,

the LED output INSERTED goes high, the part leaves the

“Insert State,” generates the “Bypass Key,” and starts

waiting for PHTM1 and PHTM2 to go low again.

CONFIGURATION 2

Concentrator Media Converter:

This configuration is selected by tying KEYGEN to ground.

There are always two fixed signal paths, one from TPINP and

TPINN to OPVCC and OPOUT, and another from OPINP

and OPINN to TPOUTP and TPOUTN. The part powers

on in the “Bypass State” where it neither applies phantom

current nor checks for a phantom wire fault. After

recognizing an “Insertion Key” at its fiber optic inputs, it

applies phantom power by providing current at PHTM1 and

PHTM2, goes to the “Phantom Wire Fault Check State,” and

starts waiting for a “Bypass Key.” At this state, the LED output

INSERTED stays low while no phantom wire fault is

detected. When the part is in the “Phantom Wire Fault Check

State” and a “Bypass Key” is recognized, the part leaves

this state, removes the phantom power, and starts waiting

for a “Insertion Key” again.

CONFIGURATION 3

Lobe or Ring Out Port Media Converter:

This configuration is selected by tying both KEYGEN and

TPINOK to ground. When the ML6680 is in the “Insert

State,” the signal paths are from TPINP and TPINN to

OPVCC and OPOUT, and from OPINP and OPINN to

TPOUTP and TPOUTN. Otherwise, the signal paths are

from TPINP and TPINN to TPOUTP and TPOUTN, and

from OPINP and OPINN to OPVCC and OPOUT. The part

powers on in the “Bypass State” and goes to the “Insert

State” after recognizing an “Insertion Key” at its fiber optic

inputs. It goes back to the “Bypass State” after recognizing

a “Bypass Key.” While it is at the “Insert State,” the LED

output INSERTED stays low.

CONFIGURATION 4

Ring In Port Media Converter:

This configuration is selected by tying KEYGEN to VCC

and TPINOK to ground. When the part is in the “Insert

State,” the signal paths are from TPINP and TPINN to

OPVCC and OPOUT, and from OPINP and OPINN to

TPOUTP and TPOUTN. Otherwise, the input at TPINP

and TPINN is routed to TPOUTP and TPOUTN, and also

to OPVCC and OPOUT. The “Insertion Key” is generated

when activity is detected at OPINP and OPINN for at least

26.5ms and, PHTM1 and PHTM2 stay low. If the

“Insertion Key Echo” is received within the following

100ms, the ML6680 goes to the “Insert State” and the LED

output INSERTED goes low. During the generation of the

“Insertion Key,” and while waiting for the “Insertion Key

Echo” the logic states of PHTM1 and PHTM2 do not have

any effect. When the part is in the “Insert State” and no

activity is detected at OPINP and OPINN for at least

26.5ms, or either PHTM1 or PHTM2 goes high, the LED

output INSERTED goes high, the part leaves the “Insert

State,” generates the “Bypass Key,” and starts waiting for

26.5ms of optical input activity again.

Low Frequency Signaling Mode

Some old implementations of discrete media converters,

use a non-standard protocol with frequencies between

1 and 10kHz. To facilitate the migration to the ML6680,

a specific operating mode is provided by grounding the

pin INSERTED. Pin KEYGEN should also be grounded to

prevent the generation of unwanted “Insertion” or “Bypass

Keys.” In this operating mode, the optical frequency

squelch circuitry is disabled and the time constant of the

amplitude squelch is significantly reduced.

For each edge of the low frequency optical input, the

ML6680 generates a pulse at the led output OPINOK.

It also generates a pulse at the TPOUTP output for each

rising edge and another at the TPOUTN output for

each falling edge.