acoektos
Newbie level 3
Hi everyone
Im trying to detect an event from some ADC data based on the Magnitude of a peak in VHDL. This should just be as simple as
But when I simulate with all data from X"FFFF" downto X"0000" I see a little inconsistency around the shift from -32768 and 32768. At the rising edge when internal_reg_in have value "1000 0000 0000 0001" (-32768) then EVENT_DETECTED signal goes low for one clock cycle (until the internal_reg_in have value "1000 0000 0000 0000" at the rising clock where it goes high again. Last I checked abs(-32768) = 32768 which is much higher than 10000 which should make the EVENT_DETECTED high, so why is it going low in my simulation?
I am using Xilinx ISE and ISim for synthesizing and simulation. I have attached two screenshots of simulation showing the problems I have seen.
Screenshot zoomed into the problem.
Screenshot of all the test from X"FFFF" downto X"0000".
I hope that someone is able to tell me why my simulation shows this behaviour and tell me what I can do to make it accept -32768 as a number for which the absolute value is larger than 10000.
Thanks in advance
Im trying to detect an event from some ADC data based on the Magnitude of a peak in VHDL. This should just be as simple as
Code:
signal EVENT_DETECTED : std_logic;
signal INTERNAL_REG_IN : signed(15 downto 0);
signal CLK : std_logic;
signal RST : std_logic;
EVENT_DETECTOR : process(RST,CLK)
if RST = '0' then
EVENT_DETECTED <= '0';
elsif RISING_EDGE(CLK) then
if abs(INTERNAL_REG_IN) > 10000 then
EVENT_DETECTED <= '1';
else
EVENT_DETECTED <= '0';
end if;
end if;But when I simulate with all data from X"FFFF" downto X"0000" I see a little inconsistency around the shift from -32768 and 32768. At the rising edge when internal_reg_in have value "1000 0000 0000 0001" (-32768) then EVENT_DETECTED signal goes low for one clock cycle (until the internal_reg_in have value "1000 0000 0000 0000" at the rising clock where it goes high again. Last I checked abs(-32768) = 32768 which is much higher than 10000 which should make the EVENT_DETECTED high, so why is it going low in my simulation?
I am using Xilinx ISE and ISim for synthesizing and simulation. I have attached two screenshots of simulation showing the problems I have seen.
Screenshot zoomed into the problem.
Screenshot of all the test from X"FFFF" downto X"0000".
I hope that someone is able to tell me why my simulation shows this behaviour and tell me what I can do to make it accept -32768 as a number for which the absolute value is larger than 10000.
Thanks in advance