Altera Cyclone IV, Device Handbook

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4–4 Chapter 4: Embedded Multipliers in Cyclone IV Devices
Operational Modes
Cyclone IV Device Handbook, February 2010 Altera Corporation
Volume 1
Table 4–2 lists the sign of the multiplication results for the various operand sign
representations. The results of the multiplication are signed if any one of the operands
is a signed value
.
Each embedded multiplier block has only one
signa
and one
signb
signal to control
the sign representation of the input data to the block. If the embedded multiplier
block has two 9 × 9 multipliers, the
Data A
input of both multipliers share the same
signa
signal, and the
Data B
input of both multipliers share the same
signb
signal.
You can dynamically change the
signa
and
signb
signals to modify the sign
representation of the input operands at run time. You can send the
signa
and
signb
signals through a dedicated input register. The multiplier offers full precision,
regardless of the sign representation.
1
When the
signa
and
signb
signals are unused, the Quartus II software sets the
multiplier to perform unsigned multiplication by default.
Output Registers
You can register the embedded multiplier output with output registers in either 18- or
36-bit sections, depending on the operational mode of the multiplier. The following
control signals are available for each output register in the embedded multiplier:
■
clock
■ clock enable
■ asynchronous clear
All input and output registers in a single embedded multiplier are fed by the same
clock, clock enable, and asynchronous clear signals.
Operational Modes
You can use an embedded multiplier block in one of two operational modes,
depending on the application needs:
■ One 18 × 18 multiplier
■
Up to two 9 × 9 independent multipliers
1
You can also use embedded multipliers of Cyclone IV devices to implement multiplier
adder and multiplier accumulator functions, in which the multiplier portion of the
function is implemented with embedded multipliers, and the adder or accumulator
function is implemented in logic elements (LEs).
Table 4–2. Multiplier Sign Representation
Data A Data B
Result
signa Value Logic Level signb Value Logic Level
Unsigned Low Unsigned Low Unsigned
Unsigned Low Signed High Signed
Signed High Unsigned Low Signed
Signed High Signed High Signed