Aeroflex Circuit Technology

SCD4418D Rev A 9/24/97 Plainview NY (516) 694-6700

2

Ohm terminations plus additional

receivers, the data bus signal pro-

duced is 7.5 volts typical 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 pro-

vides for the removal of the trans-

mitter 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

Wave-

forms,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 trans-

former (See Figure 5 for transformer

data and typical connection).

A low level at the Strobe input

inhibits the DATA and DATA out-

puts. 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