Aeroflex Circuit Technology

SCD4808 REV A 3/9/98

Plainview NY (516) 694-6700

2

receivers,

the

data

bus

signal

produced is 7.5 volts minimum P-P

at A-A’ (See Figure 5.). When both

DATA and DATA inputs are held low

or

high,

the

transmitter

output

becomes a high impedance and is

“removed” from the line. In addition,

an

overriding

“INHIBIT"

input

provides for the removal of the

transmitter output from the line. 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

1 MHz to meet Macair specifications

A-3818,

A-4905,

A-5232

and

A-5690. The transmitter may be

safely operated for an indefinite

period at 100% duty cycle into a

data bus short circuit.

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 1.05 Volts P-P and

reject signals less than 0.6 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. If unused, a 2K pull-up to

+5 Volts is recommended

DATA IN

DATA IN

INHIBIT

LINE TO LINE

OUTPUT

NOTES:

2. DATA and DATA inputs must be complementary waveforms or 50% duty cycle average, with no delays between them.

3. DATA and DATA must be in the same state during off time (both high or low).

Figure 1 Transmitter Logic Waveforms

Figure 2 Receiver Logic Waveforms

Note overlap

devices, the receiver outputs are swapped as shown by the dashed lines

level

LINE TO LINE

INPUT

DATA OUT

DATA OUT

1. Line to line waveforms illustrate Macair signals, MIL-STD-1553 signals are trapezoidal