CODEWITHSUNDEEP
vhdllogical-operatorsghdl
Adam Trhon
Adam Trhon

Reputation: 2935

GHDL: no function declarations for operator "and"

Here is my stripped example:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity queue is
    port(
        reset: in std_logic;
        input_ready: out std_logic
    );
end entity;

architecture reference of queue is
    signal queue_size: unsigned(15 downto 0);
begin
    process
    begin
            input_ready <= (reset = '0') and (queue_size < 1024);
    end process;
end architecture;

Where this line:

input_ready <= (reset = '0') and (queue_size < 1024);

produces

no function declarations for operator "and"
ghdl: compilation error

when running

ghdl -a queue.vhdl

with GHDL 0.32rc1 (20141104) [Dunoon edition] on Arch Linux.

According to VHDL operators both comparisons return boolean and there is and definition for two booleans. So what am I doing wrong?

Upvotes: 0

Views: 3148

Answers (1)

Paebbels
Paebbels

Reputation: 16221

The two sub expressions (reset = '0') and (queue_size < 1024) return a boolean value. The and operator also returns a boolean result, which you are trying to assign to a std_logic output.

The solution:

input_ready <= '1' when (reset = '0') and (queue_size < 1024) else '0';

Note: This line needs no surrounding process.

Upvotes: 4

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