simulation error

[u_stadler@yahoo.de]

hi

i wrote the following design:

http://www.pfeilheim.sth.ac.at/elektronik/Interface.vhd

behavioral simulation works fine but when i simulate post fit&route my
IO signal is undefined after reset goes high.

any ideas why? or is this design in general bad?

thanks

 

[u_stadler@yahoo.de]

on thing i forgot to ask:

when i synthesise the design it assumes that thr RD and WR signals are
clocks. how can i avoid this? is there a command?. the reason why i
don't want this is because when i want to assign package pins i will
only allow me to use clock pins for those signals.

thanks

 

[Mike Treseler]

u_stadler@yahoo.de wrote:

any ideas why? or is this design in general bad?

The design lacks a clock input and
instead uses WR and RD as clocks.

-- Mike Treseler

 

[Mike Treseler]

u_stadler@yahoo.de wrote:

when i synthesise the design it assumes that thr RD and WR signals are
clocks. how can i avoid this?

Add a clock input and use 'event with no other inputs.

-- Mike Treseler
____________________________
IN_SYNC: process(RESET, clk)
begin
if RESET = '0' then
s_In_Data <= (others => '0');
elsif rising_edge(clk) then
if WR = '1' then
s_In_Data <= s_Next_In_Data;
s_In_Count <= s_Next_In_Count;
end if;
end if;
end process IN_SYNC;

 

[u_stadler@yahoo.de]

but how can i trigger on a rising edge then?
for example i only want to copy the input on the rising edge of WR?

 

[Mike Treseler]

u_stadler@yahoo.de wrote:

but how can i trigger on a rising edge then?

make a synchronous strobe using an
AND gate, inverter and one flop.

for example i only want to copy the input on the rising edge of WR?

Use the strobe in the clocked process:

if strobe = '1' then
some_reg <= input_to_copy;
end if;

Here's a related example of counting rising edges
using a synchronous strobe:

http://home.comcast.net/%7Emike_treseler/rise_count.vhd

This uses variables instead of signals,
but it's the same idea.

-- Mike Treseler