GENERAL
rations (long or short stub). This data is converted to bi-phase
TTL and made available for decoding at the RX DATA and
RX DATA terminals. Applying a logic “1” to the STROBE input
allows data to pass through to the receiver output. Applying a
logic “0” to the STROBE input turns the receiver output OFF.
The BU-63152 is a dual redundant transmitter and receiver
packaged in a 64-pin QFP (see Figure 5). It is directly compati-
ble to Harris 15530 encoder/decoder and has internal (factory
preset) threshold levels. Requiring only a +5V power supply, the
BU-63152 is designed for use in any MIL-STD-1553 application.
The BU-63152 receiver outputs are both at a logic “0” when they
are either strobed off, or no signal is being received. This is
directly compatible with a “Harris” type of encoder/decoder.
Compatibility to a “Smiths” type of encoder/decoder may be
accomplished by swapping the RX DATA OUT and
RX DATA OUT outputs and then inverting them (see FIGURE 4).
FIGURE 1 shows a BU-63152 transceiver connected to a MIL-
STD 1553 Data Bus. Once transformer isolated, coupling to a
MIL-STD-1553 Data Bus can be either short stub (direct) or long
stub (transformer). The recommended transformer for long and
short stub coupling is Beta P/N B-3226 (through hole) or B-3227
(surface mount). There are other transformer configurations
available from Beta. Reference FIGURE 3 and TABLE 2.
BU-63152 WAVEFORMS
FIGURE 2 illustrates the waveforms for the BU-63152. Note that
DATA and DATA inputs must be complementary waveforms of
50% average duty cycle while transmitting.
TRANSMIT OPERATING MODE
The transmitter section accepts encoded TTL data and converts
it to phase-modulated differential format by means of a wave-
shaping network and driver circuitry. These driver outputs are
coupled to a MIL-STD-1553 Data Bus via a transformer which is
driven from the TX DATA OUT and TX DATA OUT terminals.
These output terminals can be put into a high impedance state
when transmitting by bringing the respective TX_INHIBIT input
to logic “1”, or by placing both inputs at the same logic level.
TABLE 3, Transmit Operating Mode, lists the functions for the
output data and input data in reference to the state of INHIBIT.
TRANSFORMERS
In selecting isolation transformers to be used with the BU-63152,
there is a limitation on the maximum amount of leakage induc-
tance. If this limit is exceeded, the transmitter rise and fall times
may increase, possibly causing the bus amplitude to fall below
the minimum level required by MIL-STD-1553. In addition, an
excessive leakage imbalance may result in a transformer
dynamic offset that exceeds 1553 specifications.
The transceivers are able to operate in a “wraparound” mode.
This allows output data to be monitored by the receiver section
and returned to the decoder where it can be checked for errors.
The maximum allowable leakage inductance is 6.0 µH, and
is measured as follows:
The side of the transformer that connects to the BU-63152 is
defined as the “primary” winding. If one side of the primary is
shorted to the primary center-tap, the inductance should be mea-
sured across the “secondary” (stub side) winding. This induc-
tance must be less than 6.0 µH. Similarly, if the other side of the
primary is shorted to the primary center-tap, the inductance mea-
sured across the “secondary” (stub side) winding must also be
less than 6.0 µH.
RECEIVER OPERATING MODE
The receiver section accepts data from a MIL-STD-1553 Data
Bus when properly coupled in either of the two possible configu-
TX Data In
TX Data In
The difference between these two measurements is the
“differential” leakage inductance. This value must be less than
1.0 µH.
LINE-TO-LINE
OUTPUT
LINE-TO-LINE
INPUT
Beta Transformer Technology Corporation (BTTC), a subsidiary
of DDC, manufactures transformers in a variety of mechanical
configurations with the required turns ratios of 1:2.5 direct cou-
pled, and 1:1.79 transformer coupled. TABLE 2 provides a list-
ing of many of these transformers.
RX Data Out
RX Data Out
Notes:
(1) TX Data In and RX Data Out are TTL signals.
(2) TX Data In inputs must be at opposite logic levels during transmission, and at
a low logic level when not transmitting.
(3) LINE-TO-LINE output voltage is measured between TX Data Out and TX Data Out.
(4) LINE-TO-LINE input voltage is measured on the Data Bus.
For further information, contact BTTC at 631-244-7393 or at
www.bttc-beta.com.
FIGURE 2. TYPICAL OPERATING WAVEFORMS
Data Device Corporation
BU-63152
www.ddc-web.com
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