User guide

System Generator for DSP User Guide www.xilinx.com 103
UG640 (v 12.2) July 23, 2010
Design Styles for the DSP48
tree:
.../sysgen/examples/dsp48/dsp48_macro.mdl
Replacing a DSP48 Macro Block with DSP48 Macro 2.0 Block
In Release 11.4, Xilinx introduced version 2.0 of the DSP Macro block. The following text
describes how to replace an existing DSP Macro block with a DSP Macro 2.0 block.
One fundamental difference of the new DSP48 Macro 2.0 block compared to the previous
version is that internal input multiplexer circuits are removed from the core in order to
streamline and minimize the size of logic for this IP. This has some implications when
migrating from an existing design with DSP48 Macro to the new DSP48 Macro 2.0. You can
no longer specify multiple input operands (i.e. A1, A2, B1, B2, etc…). Because of this, you
must add a simple MUX circuit when designing with the new DSP48 Macro 2.0 if there is
more than one unique input operand as shown in the following example.
DSP48 Macro-Based Signed 35x35 Multiplier
The following DSP48 Macro consists of multiple 18-bit input operands such as alo, ahi for
input to port A and blo, bhi for input to port B. The input operands and Opcode
instructions are specified as shown below. Notice that the multiple input operands are
handled internally by the DSP48 Macro block.