LMU18 Datasheet, PDF (1/7 Pages) LOGIC Devices Incorporated – 16 x 16-bit Parallel Multiplier

DEVICES INCORPORATED
DEVICES INCORPORATED
LMU18
LMU18 ^{16 x 16-bit Parallel Multiplier}
16 x 16-bit Parallel Multiplier
FEATURES
DESCRIPTION
u 35 ns Worst-Case Multiply Time
u Low Power CMOS Technology
u Full 32-bit Output Port —
No Multiplexing Required
u Two’s Complement, Unsigned, or
Mixed Operands
u Three-State Outputs
u 84-pin PLCC, J-Lead
The LMU18 is a high-speed, low
power 16-bit parallel multiplier.
The LMU18 is an 84-pin device
which provides simultaneous access
to all outputs.
The LMU18 produces the 32-bit
product of two 16-bit numbers.
Data present at the A inputs, along
with the TCA control bit, is loaded
into the A register on the rising edge
of CLK. B data and the TCB control
bit are similarly loaded. Loading of
the A and B registers is controlled
LMU18 BLOCK DIAGRAM
CLK
ENA
ENB
TCA
A 15-0
16
A REGISTER
TCB B15-0
16
B REGISTER
RND
by the ENA and ENB controls. When
HIGH, these controls prevent appli-
cation of the clock to the respective
register. The TCA and TCB controls
specify the operands as two’s com-
plement when HIGH, or unsigned
magnitude when LOW.
RND is loaded on the rising edge of CLK,
providing either ENA or ENB are LOW.
RND, when HIGH, adds ‘1’ to the
most significant bit position of the
least significant half of the product.
Subsequent truncation of the 16 least
significant bits produces a result
correctly rounded to 16-bit precision.
At the output, the Right Shift control (RS)
selects either of two output formats. RS
LOW produces a 31-bit product with a
copy of the sign bit inserted in the MSB
postion of the least significant half. RS
HIGH gives a full 32-bit product. Two
16-bit output registers are provided to
hold the most and least significant
halves of the result (MSP and LSP) as
defined by RS. These registers are loaded
on the rising edge of CLK, subject to the
ENR control. When ENR is HIGH, clock-
ing of the result registers is prevented.
RS
FT
ENR
MSPSEL
32
FORMAT ADJUST
16
16
RESULT
REGISTER
OEM
16
OEL
16
For asynchronous output these registers
may be made transparent by setting the
feed through control (FT) HIGH and
ENR LOW.
The two halves of the product may be
routed to a single 16-bit three-state
output port (MSP) via a multiplexer.
MSPSEL LOW causes the MSP outputs to
be driven by the most significant half of
the result. MSPSEL HIGH routes the
least significant half of the result to the
MSP pins. The MSB of the result is avail-
able in both true and complemented
form to aid implementation of higher
precision multipliers.
R 31
R 31-16
R 15-0
Multipliers
1
08/16/2000–LDS.18-O