Aeroflex Circuit Technology

SCD4469D REV A 5/21/01 Plainview NY (516) 694-6700

2

A-A’ (See Figure 5). When both

DATA and DATA inputs are held low

or

high,

the transmitter

output

impedance is low, and signal is

“removed”

from

the

line.

In

addition, an overriding “INHIBIT”

input returns the output impedance

to a high state. A logic “1” applied

to the “INHIBIT” takes priority over

the condition of the data inputs and

disables

the

transmitter.

(See

Transmitter

Logic

Waveforms,

Figure 1).

The

transmitter

utilizes

an

active filter to suppress harmonics

above

1MHz

to

meet

H009

specification. The transmitter may

be safely operated for an indefinite

period

with

the

output

short

circuited at 100% duty cycle.

Receiver

The Receiver section accepts

bi-phase differential data at the

input

and

produces

two

TTL

signals at the output. The outputs

are DATA and DATA, and represent

positive and negative excursions of

the input beyond a pre-determined

threshold

(See

Receiver

Logic

Waveforms, Figure 2).

The

internal

threshold

is

nominally set to detect data bus

signals exceeding 1.0 Volts P-P

when used with a 1:1 turns ratio

transformer

(See

Figure

5

for

transformer

data

and

typical

connection).

A low level at the Strobe input

inhibits

the

DATA

and

DATA

outputs. The strobe is internally

pulled up, therefore a pull resistor

is not needed.

Figure 1A – Tx Output Truth Table

DATA

DATA

INHIBIT

OUTPUT

X

X

H

High Z

HH

L

Low Z

(No signal)

LL

L

HL

L

Low Z

(Signal)

LH

L

DATA IN

DATA IN

INHIBIT

LINE TO LINE

OUTPUT

Figure 1B - Transmitter Logic Waveforms

Figure 2 - Receiver Logic Waveforms

Note overlap

LINE TO LINE

INPUT

Rx DATA OUT

Rx DATA OUT

Notes: 1. Data and DATA inputs must be complementary waveforms or 50% duty cycle average, with no delays between them, and in the same state during

the off time (both high and low).

2. Region 1; no output signal, High Z state, (Receive Mode), Region 2; No Output signal, Low Z state, Region 3; Transmitter signal

on, low Z (Transmitter mode), Region 4; No Output signal, Low Z state, (Terminate Mode).

Region

1

2

34

1