This block is listed in the following Xilinx® Blockset libraries: Floating-Point, Math, and Index.
The Xilinx MultAdd block performs both fixed-point and floating-point multiply and addition with the a and b inputs used for the multiplication and the c input for addition or subtraction.
If the MultAdd inputs are floating point, then inputs a,b, and c must be of the same data type. If the inputs are fixed point, then the port c binary point must be aligned to the sum of the port a and port b binary points.
The block parameters dialog box can be invoked by double-clicking the icon in your Simulink® model.
- Basic tab
- Parameters specific to the Basic tab are as follows.
- Specifies that an addition will be performed after multiplication.
- Specifies that a subtraction will be performed after multiplication.
- Addition or subtraction
- Adds a subtract port to the block, which controls whether the operation following multiplication is addition or subtraction (subtract High = subtraction, subtract Low = addition).
- Optional Ports
- Provide enable port
- Adds an active-High enable port to the block interface.
This defines the number of sample periods by which the block's output is delayed. The latency values you can set depend on whether you are performing fixed point or floating point arithmetic:
- For fixed point arithmetic, you can only specify a latency of 0 (for no latency) or -1 (for maximum/optimal latency). If you have added an enable port to the block interface, you can only specify a latency of -1 for fixed point arithmetic.
- For floating point arithmetic, you can only specify a latency of 0 (for no latency) or a positive integer. If you have added an enable port to the block interface, you can only specify a positive integer for floating point arithmetic.
See the LogiCORE IP Multiply Adder v3.0 Product Guide for details on latency in the block.
- Output tab
Parameters specific to the Output tab are as follows.
- This parameter allows you to specify the output precision for
fixed-point arithmetic. Floating point arithmetic output will
always be Full precision.
- The block uses sufficient precision to represent the result without error.
- User Defined
- If you do not need full precision, this option allows you to specify a reduced number of total bits and/or fractional bits.
- Fixed-point Output Type
- Arithmetic type
- Signed (2’s comp)
- The output is a Signed (2’s complement) number.
- The output is an Unsigned number.
Other parameters used by this block are explained in the topic Common Options in Block Parameter Dialog Boxes.
LogiCORE IP Multiply Adder v3.0