altfp_mult Megafunction

altfp_mult (Floating Point Multiplier) Megafunction

Parameterized floating point multiplier megafunction. Altera^® recommends that you use the altfp_mult function instead of any other type of floating point multiplier function.

Altera also recommends instantiating this function as described in Using the MegaWizard^® Plug-In Manager.

This topic contains the following information:

AHDL Function Prototype (also applies to Verilog HDL)
VHDL Component Declaration
VHDL LIBRARY-USE Declaration (not required if the VHDL Component Declaration is used)
Port Descriptions
Parameter Descriptions
Truth Table/Functionality
Resource Usage
Floating Point Format

AHDL Function Prototype (port name and order also apply to Verilog HDL):

FUNCTION altfp_mult (clock, clk_en, aclr, dataa[WIDTH_EXP+WIDTH_MAN..0], 
      datab[WIDTH_EXP+WIDTH_MAN..0] )
   WITH (WIDTH_EXP, WIDTH_MAN, DEDICATED_MULTIPLIER_CIRCUITRY )
   RETURNS (result[WIDTH_EXP+WIDTH_MAN..0], overflow, underflow, zero, denormal,
      indefinite, nan );

VHDL Component Declaration:

COMPONENT altfp_mult
   GENERIC 
      (WIDTH_EXP                       : INTEGER := 8;
      WIDTH_MAN                        : INTEGER := 23;
      DEDICATED_MULTIPLIER_CIRCUITRY   : STRING  := "AUTO";
      LPM_HINT                         : STRING  := "UNUSED";
      LPM_TYPE                         : STRING  := "ALTFP_MULT");

    PORT (clock                           : IN STD_LOGIC;
         clk_en                           : IN STD_LOGIC := '1';
         aclr                             : IN STD_LOGIC := '0';
         dataa, datab                     : IN STD_LOGIC_VECTOR (WIDTH_EXP + WIDTH_MAN DOWNTO 0);
         result                           : OUT STD_LOGIC_VECTOR (WIDTH_EXP + WIDTH_MAN DOWNTO 0);
         overflow, underflow, zero,
            denormal, indefinite, nan     : OUT STD_LOGIC;);

END COMPONENT;

VHDL LIBRARY-USE Declaration

LIBRARY altera_mf;
USE altera_mf.altera_mf_components.all;

Port Descriptions:

INPUT PORTS

Port Name	Required	Description	Comments
`clock`	Yes	Clock input to the multiplier.
`clk_en`	No	Clock enable for the multiplier.
`aclr`	No	Asynchronous clear for the multiplier.
`dataa`	Yes	Data input to the multiplier.	Input port `[WIDTH_EXP + WIDTH_MAN DOWNTO 0]` wide.
`datab`	Yes	Data input to the multiplier.	Input port `[WIDTH_EXP + WIDTH_MAN DOWNTO 0]` wide.

OUTPUT PORTS

Port Name	Required	Description	Comments
`result`	Yes	Multiplier output port.	Output port `[WIDTH_EXP + WIDTH_MAN DOWNTO 0]` wide.
`overflow`	No	Overflow port for the multiplier.
`underflow`	No	Underflow port for the multiplier.
`zero`	No	Zero port for the multiplier.
`denormal`	No	Denormal port for the multiplier.
`indefinite`	No	Indefinite port for the multiplier.
`nan`	No	Nan port for the multiplier.

Parameter Descriptions:

Parameter	Type	Required	Comments
`WIDTH_EXP`	Integer	No	Specifies the value of the exponent. If omitted, the default is `"8"`. The Bias of the exponent is always set to `2 * WIDTH_EXP - 1` (i.e. `-127` for single precision floating point format and `-1023` for double precision floating point format). `WIDTH_EXP` must be `8` for single precision floating point format or a minimum of `11` for double precision and single extended precision floating point format. `WIDTH_EXP` must less than `WIDTH_MAN`. The sum of `WIDTH_EXP` and `WIDTH_MAN` must be less than `64`.
`WIDTH_MAN`	Integer	No	Specifies the value of the mantissa. If omitted, the default is `"23"`. When `WIDTH_EXP` is `8` and the floating point format is single precision, the `WIDTH_MAN` value must be `23`. Otherwise, the value of `WIDTH_MAN` must be a minimum of `31`. The `WIDTH_MAN` value must always be greater than the `WIDTH_EXP` value. The sum of `WIDTH_EXP` and `WIDTH_MAN` must be less than `64`.
`DEDICATED_MULTIPLIER_CIRCUITRY`	String	No	Specifies whether to use dedicated multiplier circuitry. Values are `"AUTO"`, `"YES"`, or `"NO"`. If omitted, the default is `AUTO`. If a device does not have dedicated multiplier circuitry, the `DEDICATED_MULTIPLIER_CIRCUITRY` parameter has no effect and defaults to `NO`.
`LPM_HINT`	String	No	Allows you to assign Altera-specific parameters in VHDL Design Files (.vhd). The default is `"UNUSED"`.
`LPM_TYPE`	String	No	Identifies the library of parameterized modules (LPM) entity name in VHDL Design Files.

Truth Table/Functionality:

Inputs		Outputs
`dataa[]`	`datab[]`	`result[]`	`overflow`	`underflow`	`zero`	`denormal`	`indefinite`	`nan`
Normal	Normal	Normal	0	0	0	0	0	0
Normal	Normal	Denormal	0	1	0	1	0	0
Normal	Normal	Infinity	1	0	0	0	0	0
Normal	Normal	Zero	0	1	1	0	0	0
Normal	Denormal	don't care	0	0	0	0	1	0
Denormal	Normal	don't care	0	0	0	0	1	0
Denormal	Denormal	don't care	0	0	0	0	1	0
Zero	Normal	Zero	0	0	1	0	0	0
Zero	Denormal	Zero	0	0	1	0	0	0
Zero	Zero	Zero	0	0	1	0	0	0
Normal	Zero	Zero	0	0	1	0	0	0
Denormal	Zero	Zero	0	0	1	0	0	0
Infinity	Normal	Infinity	1	0	0	0	0	0
Infinity	Denormal	Infinity	1	0	0	0	0	0
Infinity	Infinity	Infinity	1	0	0	0	0	0
Infinity	Zero	NaN	0	0	0	0	0	1
Normal	Infinity	Infinity	1	0	0	0	0	0
Denormal	Infinity	Infinity	1	0	0	0	0	0
Zero	Infinity	NaN	0	0	0	0	0	0
NaN	Normal	NaN	0	0	0	0	0	1
NaN	Denormal	NaN	0	0	0	0	0	1
NaN	Zero	NaN	0	0	0	0	0	1
NaN	Infinity	NaN	0	0	0	0	0	1
NaN	Nan	NaN	0	0	0	0	0	1
Normal	NaN	NaN	0	0	0	0	0	1
Denormal	NaN	NaN	0	0	0	0	0	1
Zero	NaN	NaN	0	0	0	0	0	1
Infinity	NaN	NaN	0	0	0	0	0	1

Resource Usage:

Design

Design Results

Device Family	Precision Type	Dedicated Multiplier Circuitry
Stratix^™ Note (1)	Single	Yes
	Single	No
	Double	Yes
	Double	No
APEX^™ 20K Note (2)	Single	Not Applicable
	Double	Not Applicable

f_MAX	Logic Cells	DSP Blocks 9-Bit Elements
97.59 MHz	627	8
87.03 MHz	1614	0
70.20 MHz	1450	26
62.51 MHz	5613	0
57.37 MHz	1659	0
35.94 MHz	5763	0

Floating Point Format:

Location Label	Description	Bits Position
Sign	Sign bits of a floating point number.	`WIDTH_EXP + WIDTH_MAN`
Exponent	Exponent bits of a floating point number.	`(WIDTH_EXP + WIDTH_MAN - 1) DOWNTO WIDTH_MAN`
Mantissa	Mantissa bits of a floating bit number.	`(WIDTH_MAN - 1) DOWNTO 0`

Example:

Location	Single Precision	Double Precision	Single Extended Precision
Location	`WIDTH_EXP = 8 WIDTH_MAN = 23`	`WIDTH_EXP = 11 WIDTH_MAN = 52`	`WIDTH_EXP = 11 WIDTH_MAN = 31`	`WIDTH_EXP = 20 WIDTH_MAN = 38`
Sign	`dataa[31]`	`dataa[63]`	`dataa[42]`	`dataa[58]`
	`datab[31]`	`datab[63]`	`datab[42]`	`dataa[58]`
	`result[31]`	`result[63]`	`result[42]`	`result[58]`
Exponent	`dataa[30..23]`	`dataa[62..52]`	`dataa[41..31]`	`dataa[57..38]`
	`datab[30..23]`	`datab[62..52]`	`datab[41..31]`	`datab[57..38]`
	`result[30..23]`	`result[62..52]`	`result[41..31]`	`result[57..38]`
Mantissa	`dataa[22..0]`	`dataa[51..0]`	`dataa[30..0]`	`dataa[37..0]`
	`datab[22..0]`	`datab[51..0]`	`datab[30..0]`	`datab[37..0]`
	`result[22..0]`	`result[51..0]`	`result[30..0]`	`result[37..0]`

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