when coupled to the data bus with a
1:2.5 ratio transformer, isolated on
the data bus side with two 52.5 Ohm
fault isolation resistors, and loaded
by two 70 Ohm terminations, the
data bus signal is typically 7.0 volts
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
Waveform,
Figure
1.)
The
Transmitter may be safely operated
for an indefinite period with the bus
(point A-A') short circuited at 100%
duty cycle.
negative excursions of the input
beyond
a
pre-determined
threshold.(See Receiver Logic
Waveform. Figure 2.)
The pre-set internal thresholds
will detect data bus signals
exceeding 1.20 Volts P-P and
reject signals less than 0.6 volts
P-P when used with a 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
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
Figure 1 — Transmitter Logic Waveforms Idealized
*
DATA IN
DATA IN
INHIBIT
LINE TO LINE
OUTPUT
Note:
DATA and DATA inputs must be complementary waveforms or 50% duty cycle average, with no delays between them,
and must be in the same state during off times (both high or low).
Figure 2 — Receiver Logic Waveforms Idealized
*
LINE TO LINE
INPUT
STROBE
DATA OUT
DATA OUT
* See Figure 7 For Actual Waveforms
Aeroflex Circuit Technology
Note overlap
2
SCD4454 REV A 3/17/99 Plainview NY (516) 694-6700
AEROFLEX [ AEROFLEX CIRCUIT TECHNOLOGY ]
