envelope_gen is modified due to the following bug. The output ENV_OUT is not
properly latched. So output turns to zero before the pulse count reaches to
zero. So ENV_OUT_PREV signal is added to hold the previous state of the
ENV_OUT. Its just an SR latch.
gaurd.vhd is modified due to the typographical error
waveform_gen_top.vhd -> few signal declerations are missing were added.
warning due to
DT: dead_time_controller
port map (
	PULSE_IN => not CH1;
         );
this was changed to warning a signal is defined for < not CH1 > as CH1_NOT
The memory controller wait_for_load state is added. TODO need to add
the information of the state more correctly.
Waveform_gen_top.vhd in this a monostable is added to avoid re-triggering
due to the bounce of the circuit.
waveform_gen_top.vhd: DEBUG signal included to debug the internals of the
waveform_gen_top.vhd module. This is not the final version of the file
need to clean up the file
envelope_gen.vhd: the check for envelope to end i.e. pulse_count = 1 is changed
to pulse count = 0. need to check the integrity of the change.