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
- 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 Multiply Adder LogiCORE IP Product Guide (PG192) 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.