LPM hints
Author: Crystal Jorundson
Max+PLUS II recommends using its LPM macros when designing for Altera PLDs. To enhance
the use of LPM's, this application note includes notes on various lpm components.
Help notes are provided to clarify any uncertainties about the Altera help files, as well as including
any known errors in the help file component declarations.
Resource Usage Tables provide logic cell and speed information for various configurations of an
lpm component. They are specific to the EP10K20RC240-4, compiled on the workstation
version of Max+Plus II. This is to enhance the student's reference materials, allowing for a
quicker estimate of the resource usage of a design. Automatic Register Packing and Automatic
I/O Cell Registers were selected from the "Global Project Logic Synthesis" option for all
compilations. Compilations are shown for both routability and speed.
A VHDL template is provided for each lpm component examined. In most cases this is the
component used to obtain a minimum clock period less than 40 ns. It may be one of the special
cases (eg. Constant multipier input to lpm_mult).
Contents
General hints
Simulation hints
lpm_mult
lpm_add_sub
Fast Global Project Synthesis Style
The fast synthesis style is useful when you want to make use of the carry chains internal to
the FLEX10K logic cells. This will decrease the logic cell count for some arithmetic
components. See the Resource Usage Tables for examples.
LPM_PIPELINE
If you specify the LPM_PIPELINE parameter to be a high value (like 20 for a 16-bit adder),
the compiler will provide Info on the number of pipelines you should use for best performance/untilization.
See the Resource Usage Tables for examples.
Setting the clock period
If you have difficulty setting the clock period, check if "Show Grid" is selected under the waveform "Options" menu. If it is, check the "Grid Size" and make sure it is equal to one half period of the desired clock rate. For example, for a clock rate of 40 ns, either don't show the grid or show the grid with a grid size of 20ns.
Max+PLUS II recommends using its LPM macros when designing for Altera PLDs. The
LPM_multiplier is useful for a variety of applications including various DSP algorithms.
Max+Plus II Help Notes
Resource Usage Tables
VHDL Template
Max+Plus II Help Notes
Resource Usage Tables
VHDL Template
Last Updated on March 13, 1999 by Crystal Jorundson, 243412