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I must say Im confused, as in this case its hard to tell where it is declared, at port1 or port2.. Maybe synthesis is just as confused and dont care about init state :)
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Here is a piece of Altera code for rom inference:
-- Declare the ROM signal and specify a default value. Quartus II
-- will create a memory initialization file (.mif) based on the
-- default value.
signal rom : memory_t := init_rom;
begin
process(clk)
begin
if(rising_edge(clk)) then
q_a <= rom(addr_a);
q_b <= rom(addr_b);
end if;
end process;
end rtl;
The reading of ports q_a or q_b can be across two modules but the rom array (called rom) occurs only once.
But I must be cautious here as templates for inference need to be adhered to well.
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I guess this way of thinking is only "graphically valid" if you draw a "wire" between the register output and the wire at next entity. My first thought was that a wire is just a wire, not a "semiconductor" and hence I thought it would be identical to register output, but Im probably wrong. Maybe synthesis should just refuse to set initial value to a wire.
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If I assign B <= A then in the final synthesis I expect both nodes will optimise to one and the notion of wire will vanish but at code level the compiler will need to look at how the user describes their drive. In this case no gating is involved and it seems it ignores initial value on B.
If additionally I assign A <= B then obviously I need first to resolve the double drive on A and the compiler I assume will propagate initial value of B to A according to my logic if it applies as initial state.
So my view is that A and B nodes exist as separate nodes first until the compiler realises that both are just identical at the end and require no gating but refuses to respect initial value on B.
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Nice to hear history from the locals mouth! :) I missed that local history part on my visit. On my trip, the guides were mainly American and Norwegian oilbusiness men. We had a Kurd from Erbil with us but he told us more abour Kurdistan in general. I hope I can visit the area again one day with a different focus and more time on the hand :)
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Thanks for your interest. Best time of visits would be spring March ~ June. Not summer as you will be attacked by armies of mosquitoes.
Honored Contributor
