CDPCLK4 datasheet(57/274 Pages) ALTERA

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Chapter 4: Embedded Multipliers in the Cyclone III Device Family

4–5

Operational Modes

December 2011

Altera Corporation

Cyclone III Device Handbook

Volume 1

Table 4–3 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 using 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-bit × 18-bit multiplier

■

Up to two 9-bit × 9-bit independent multipliers

Table 4–3. Multiplier Sign Representation

Data A

Data B

Result

signa Value

Logic Level

signb Value

Logic Level

Unsigned

Low

Unsigned

Low

Unsigned

Low

Signed

High

Signed

High

Unsigned

Low

Signed

High

Signed

High

Signed

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