EP4CE30F29C7N Datasheet, PDF (58/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

4–4
Chapter 4: Embedded Multipliers in Cyclone IV Devices
Operational Modes
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.
Table 4–2. Multiplier Sign Representation
Data A
Data B
signa Value
Unsigned
Unsigned
Signed
Signed
Logic Level
Low
Low
High
High
signb Value
Unsigned
Signed
Unsigned
Signed
Logic Level
Low
High
Low
High
Result
Unsigned
Signed
Signed
Signed
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).
Cyclone IV Device Handbook,
Volume 1
February 2010 Altera Corporation