Instruction manual

BD416 • 4
Introduction
The BD416 is a simple 4 line binary input to one of 16 lines output interface.
The output can be configured to latch the output when a valid data signal is
applied. The valid data signal may be either an active high or active low logic
level input. In the latched output configuration the output may be set to
initialize to a set, output line “0” low, or reset, output line “15” low, state at
power-up. In non-latched configuration the output initializes to match the
input binary setting on power-up and simply follows the input. The binary
input is active high 5 volt logic level.
BD416 Circuit Operation
If you look on the left side of the schematic you will see the 4 binary input
lines, B0, B1, B2, B3 and “VALID DATA”. The input may be applied to J1, J2
and/or J5. First we’ll discuss the non-latched configuration. A binary code is
applied to B0 thru B3. These 4 lines are applied to U4 pins 3, 6, 10 and 13
respectively. U4 is a quad 2 input multiplexer which means it’s like 4, SPDT
switches. It simply selects one of the input signals on each switch. The
switches are controlled by the “SEL” signal, U4 pin 1. With a high level
applied to U4 pin 1, that’s when no jumper is installed on “LATCH” jumper
H2, the signals applied to the BD416 inputs are directly selected. The
outputs of U4 are pins 4, 7, 9 and 12 and are connected to U3 pins 10,21, 22
and 23 respectively.
U3 is a 4 line to 16 line decoder. It decodes the 4 binary input lines to one of
16 output lines just like it’s name suggests. Only one of the 16 output lines is
low according to the binary code applied to the inputs. This is probably a
good time to explain a little about binary signals.
A binary signal has only two conditions. It can be either a high level, usually
called a “1”, or it can be a low level usually called a “0”. Since we need to be
able to represent 16 conditions and have only two levels to work with we will
need 4 separate binary signal lines. Since most of us are use to the decimal,
or 10’s base counting system we’ll assign each of the 4 binary lines a value.
For the BD416 input B0 will have a value of 1, B1 will equal 2, B2 will be 4
and B3 will equal 8. In order to figure out what the input signal value is in
decimal all you need to do is add the above values of each line that is set to
a 1 together. So if B3 = 0, B2 = 1, B1 = 0 and B1 = 1 the decimal value will
be 0 + 4 + 0 + 1 which equals 5 and output 5 will be low. A binary
representation of this value is written in the order, B3, B2, B1, B0 or “0101”
for this example. For another example the decimal number 9 would be
written as “1001” in binary. Just add 8 + 0 +0 +1 = 9. A table listing all 16
input and output combinations is given in TABLE 1 below.