-- Copyright(C) 2006 by Xilinx, Inc. All rights reserved. 
-- The files included in this design directory contain proprietary, confidential information of 
-- Xilinx, Inc., are distributed under license from Xilinx, Inc., and may be used, copied 
-- and/or disclosed only pursuant to the terms of a valid license agreement with Xilinx, Inc. 
-- This copyright notice must be retained as part of this text at all times. 


Description:
The design is based upon the BCD-counter and the 7-segment LED display.
The method of measurement is comparing the input signal frequency with
the reference clock signal that is faster than the measured signal.
The measurment is started by setting the START signal to '1'. Setting
START back to '0' finishes the measurment and resets the meter.
The design includes 3 blocks described as behavioral VHDL code
that are synthesized and implemented in a Xilinx FPGA.

Project FREQM is a simple implementation of a frequency meter with 
the BCD-counter and the 7-segment LED display.
 
Design Type: ISE (chip 3S100E VQ100 -4)

Inputs:
        FINPUT - measured frequency clock input
	  FPATTERN - reference frequency clock input
	  START - input logical signal starting the measurement, active HIGH
        RESET - asynchronous reset, active in HIGH.

Outputs:
        four-positions 7-segment LED display
	  LED_D[6:0] - the most significant decimal digit 
	  LED_C[6:0] - 
	  LED_B[6:0] - 
	  LED_A[6:0] - the least significant decimal digit
	  FULL - counter overflow flag

Simulation:
Simulation requires the following libraries:
Unisims
Simprims

Behavioural and RTL Simulation done using VHDL Testbench (freqm_tb.vhd).

NOTE: If you are trying to run this example in a read-only location,    
the design hierachy will not display properly. Please copy the example  
project to a new location by using either Project Save As... from the File menu
pulldown in ISE or some other method of your choice. Copy the example to a location
where you have write permissions and the hiearchy will display properly. 

For support information and contacts please see:

	http://www.xilinx.com/support
or
	http://www.xilinx.com/support/services/contact_info.htm
