10761A Multiplier Block Diagram - HP 5501A Operating And Service Manual

3.19 10761A Multiplier
The 10761A Multiplier card is used only with the English/Metric system. Its main purpose is to
perform the conversion of uncompensated fringe (quarter-wave) displacement data to either
metric units (in millimetres) or English units (in inches) for output to a controller.
Figure 3-76 is a block diagram of the multiplier card. The input buffer accepts and holds data
available from the coupler backplane. This may be velocity-of-light information from a com-
pensation interface card (described later), displacement information from a counter card, or
any other applicable backplane data. The next part of the multiplier is a group of AND gates
used a s data control for the magnitude data stored in the input buffer. These gates control the
add-shifthhift- only function (multiplication is accomplished by repeated shifting and adding).
From here the data goes to the adder-shifter section of the card. The inputs to the adder are
the outputs of the AND gates and the output of the accumulator. The resulting addition is fed
back to the inputs of the accumulator, which is a 29-bit register. The 29th bit is an overflow
bit used to indicate that the result of multiplication has a magnitude greater than 2 8 bits. The
multiplier register i s a shift register that can be loaded from the accumulator or from a con-
stants ROM (read-only-memory) which contains
all
the conversion constants for the multi-
plier. This shift register's least significant bit controls the input buffer AND gates.
Besides the main adder there is a four-bit decimal point adder that handles the conversion of
the decimal point code for the appropriate measurement units. These circuits are directed by
the control logic, which interprets backplane instructions and controls the execution of indi-
cated operations. The control logic has a 10 MHz clock, which allows a complete multiplication
in less than 5 microseconds.
Instructions recognized by the binary multiplier card include reset, English units, metric units,
velocity-of-light (VOL) output, counter output, and multiplier output. The VOL output in-
c.onsIan1.s
outp
0
Lines
IF
I
Accumulator
Instruction hcodw an
Control C i r m b
Figure 3-76. 70767A Multiplier Block Diagram