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Multiply-Accumulate

Perform a multiply-accumulate operation on the inputs

  • Library:
  • HDL Coder / HDL Operations / Multiply-Accumulate

Description

The Multiply-Accumulate block performs this operation on inputs a and b, and bias c, to compute result dataOut.

dataOut = sum(a.* b) + c

By default, the block operates in the vector mode. The inputs a and b can be scalars or vectors. The default bias value, c, is equal to zero, and the block computes the dot product of inputs a and b. You can specify a nonzero value for c using Dialog or Input port as the Source. The block adds this bias to the dot product of a and b. The multiplication operation is full precision irrespective of the Output data type setting. The Output data type and Integer rounding mode settings apply to the addition operation.

By using the Operation Mode setting, you can specify streaming modes of operation for the Multiply-Accumulate block. For HDL code generation, when you use the streaming operation mode, input scalar values to the block. The block has two streaming modes: Streaming - using Start and End ports and Streaming - using Number of Samples. When you select these streaming modes, you can specify the control signals to use with the mode. The control signals specify when to start and end accumulation, and when the output is valid.

Ports

Input

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Port to provide input to the block.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port to provide input to the block.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean | fixed point | enumerated | bus

Port to provide the bias signal to the block. The block adds this bias to the inputs. Make sure that the bias signal data type matches that of the dot product of the inputs.

Dependencies

To enable this port, set Source to Input port.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port to provide the control signal to start accumulation. It is recommended that you use a boolean data type signal as input to the port. To start obtaining the accumulated output value from the dataOut signal, both startIn and validIn signals must be high. The dataOut signal produces the accumulated result from the next clock cycle.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port to provide the control signal to indicate that the input signal is valid for accumulation. It is recommended that you use a boolean data type signal as input to the port. To start obtaining the accumulated output value from the dataOut signal, both validIn and startIn signals must be high. The dataOut signal produces the accumulated result from the next clock cycle. The validIn signal has higher priority than startIn and endIn signals.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports or Streaming - using Number of Samples.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port to provide the control signal to indicate end of accumulation. You can use the startIn and endIn signals with the validIn signal to indicate a frame that contains the accumulated output.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports and then select End input and output ports.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Output

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Port that generates the output data from the multiply-accumulate operation. By default, the block uses the Vector mode of operation and computes the dot product of the input signals, and adds the bias to produce the result. If you specify a streaming mode of operation as Operation Mode, the value of the dataOut signal depends on the control signals that you provide. The data type of the output signal is same as that of the accumulator.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port that generates output control signal to indicate the start of accumulation. When both validIn and startIn are high, the startOut signal becomes high in the next clock cycle. The clock cycle at which startOut becomes high indicates the start of a frame and that the dataOut signal has started producing valid accumulated output.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports and then select Start output port.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port that generates the output control signal to indicate that the dataOut signal is valid. When the validIn signal becomes high , the validOut signal becomes high in the next clock cycle and indicates that the dataOut is valid.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports and then select Valid output port.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port that generates the output control signal to indicate the end of accumulation. You can use the clock cycles between when the startOut signal becomes high and when the endOut signal becomes high to indicate a valid frame that contains the accumulated output.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports and then select End input and output ports.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Port that generates the output control signal to indicate number of samples to accumulate. The value of this signal increases from 1 to the value that you specify for Number of Samples. As long as the validIn signal is high, the countOut increments by 1 every clock cycle.

Dependencies

To enable this port, set Operation Mode to Streaming - using Number of Samples and then select Count output port.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

Parameters

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You can specify the Operation Mode as:

  • Vector: You can use scalars or vectors as inputs. The block performs the dot product of the inputs u1 and u2 and adds bias k to produce the result.

  • Streaming - using Start and End Ports: Use scalar inputs for HDL code generation. In this mode, you can use the startIn and endIn control signals to determine when to start and stop accumulation. The output data is valid when validIn is high.

  • Streaming - using Number of Samples: Use scalar inputs for HDL code generation. In this mode, you can specify the Number of Samples and use the countIn control signal to determine when to start and stop accumulation. The output data is valid when validIn is high.

Programmatic Use

Block parameter: opMode
Type: character vector
Value: 'Vector' | 'Streaming - using Start and End Ports' | 'Streaming - using Number of Samples'
Default: 'Vector'

You can specify the bias with:

  • Source as Dialog. Then, specify the Value.

  • Source as Input port. This setting creates an external input port c to input the bias signal to the block.

Programmatic Use

Block parameter: initValueSetting
Type: character vector
Value: 'Dialog' | 'Input port'
Default: 'Dialog'

If you set Source as Dialog, you can specify the initial value by using the initValue2 setting.

Block parameter: initValue2
Type: character vector
Value: An integer greater than or equal to zero
Default: '0.0'

You can specify the Number of Samples to specify a frame containing the number of samples of valid accumulated output dataOut.

Dependencies

To enable this port, set Operation Mode to Streaming - using Number of Samples.

Programmatic Use

Block parameter: num_samples
Type: character vector
Value: An integer greater than or equal to zero
Default: '2'

Set the output data type to:

  • A rule that inherits a data type, such as Inherit: Same as first input.

  • A built-in data type, such as single or int16.

  • The name of a data type object. for instance, a Simulink.NumericType object.

  • An expression that evaluates to a valid data type, for example, fixdt(1,16,0)

The streaming modes do not suuport Inherit: Inherit via internal rule. When you set the Output data type, you can use the Data Type Assistant. To display the assistant, click the Show data type assistant .

Programmatic Use

Block parameter: OutDataTypeStr
Type: character vector
Default: {'Inherit: Inherit via internal rule'}

To see possible values that you can specify for this parameter, see Block-Specific Parameters.

Specify the rounding action as:

Ceiling

Rounds positive and negative numbers toward positive infinity. Equivalent to the MATLAB® ceil function.

Convergent

Rounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™ convergent function.

Floor

Rounds positive and negative numbers toward negative infinity. Equivalent to the MATLAB floor function.

Nearest

Rounds the number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer nearest function.

Round

Rounds number to the nearest representable value. If a tie occurs, rounds positive numbers toward positive infinity and rounds negative numbers toward negative infinity. Equivalent to the Fixed-Point Designer round function.

Simplest

Chooses between rounding toward floor and rounding toward zero to generate rounding code that is as efficient as possible.

Zero

Rounds number toward zero. Equivalent to the MATLAB fix function.

Programmatic Use

Block parameter: RndMeth
Type: character vector
Default: {'Floor'}

To see possible values that you can specify for this parameter, see Block-Specific Parameters.

Control generation of the validOut output port. This port indicates whether dataOut is valid.

off

Does not display the validOut output port.

on

Display the validOut output port.

Dependencies

To enable this port, set Operation Mode to Streaming - using Number of Samples or Streaming - using Start and End Ports.

Programmatic Use

Block parameter: validOut
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Control generation of the endIn input port and the endOut output port. The ports indicate the end of a frame containing valid accumulation output.

off

Does not display the endIn input port and the endOut output port.

on

Display the endIn input port and the endOut output port.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports.

Programmatic Use

Block parameter: endInandOut
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Control generation of the startOut output port. This port generates the startOut signal that indicates the start of a frame containing valid accumulated output.

off

Does not display the startOut output port.

on

Display the startOut output port.

Dependencies

To enable this port, set Operation Mode to Streaming - using Start and End Ports.

Programmatic Use

Block parameter: startOut
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Control generation of the countOut output port. This port generates the counter that indicates a frame containing valid samples.

off

Does not display the countOut output port.

on

Display the countOut output port.

Dependencies

To enable this port, set Operation Mode to Streaming - using Number of Samples.

Programmatic Use

Block parameter: countOut
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Block Characteristics

Data Types

double | single | base integer | fixed point | bus

Sample Time

Inherit

Direct Feedthrough

Yes

Multidimensional Signals

Scalar

Variable-Size Signals

Yes

Zero-Crossing Detection

No

Algorithms

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Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Fixed-Point Conversion
Convert floating-point algorithms to fixed point using Fixed-Point Designer™.

Introduced in R2017b