Output Registers; Operational Modes - Altera Cyclone IV Device Handbook

4–4
Table 4–2
representations. The results of the multiplication are signed if any one of the operands
is a signed value.
Table 4–2. Multiplier Sign Representation
signa 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).
Cyclone IV Device Handbook,
Volume 1
lists the sign of the multiplication results for the various operand sign
Data A
Logic Level
Unsigned Low
Unsigned Low
Signed High
Signed High
Chapter 4: Embedded Multipliers in Cyclone IV Devices
Data B
signb Value Logic Level
Unsigned Low
Signed High
Unsigned Low
Signed High
February 2010 Altera Corporation
Operational Modes
Result
Unsigned
Signed
Signed
Signed