Error 10327: Can't determine definition of operator ""-""

Altera_Forum · ‎06-21-2011

Hi!

I'm getting this error all the time... and I don't know how to solve this because i'm still a rookie e this thing. Can anybody help me with that and tell me what i'm doing wrong?

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Code:

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.all;

USE IEEE.STD_LOGIC_ARITH.all;

USE IEEE.STD_LOGIC_SIGNED.all;

ENTITY Rec_dados IS

PORT( RXD : IN STD_LOGIC;

clock_115KHz : IN STD_LOGIC;

data_ready : OUT STD_LOGIC;

accx_out : OUT STD_LOGIC_VECTOR(15 DOWNTO 0);

accy_out : OUT STD_LOGIC_VECTOR(15 DOWNTO 0);

accz_out : OUT STD_LOGIC_VECTOR(15 DOWNTO 0));

END Rec_dados;

ARCHITECTURE Behavior OF Rec_dados IS

SIGNAL count : STD_LOGIC_VECTOR(6 DOWNTO 0);

SIGNAL accx_out_int, accy_out_int, accz_out_int : STD_LOGIC_VECTOR(15 DOWNTO 0);

BEGIN

PROCESS

BEGIN

WAIT UNTIL clock_115KHz'EVENT and clock_115KHz = '1';

IF count < 32 THEN

count <= count + 1;

END IF;

IF count > 31 AND count < 48 THEN

accx_out_int(47 - count) <= RXD;

count <= count + 1;

END IF;

IF count > 47 AND count < 64 THEN

accy_out_int(63 - count) <= RXD;

count <= count + 1;

END IF;

IF count > 63 AND count < 80 THEN

accz_out_int(79 - count) <= RXD;

count <= count + 1;

END IF;

IF count > 79 THEN

accx_out <= accx_out_int;

accy_out <= accy_out_int;

accz_out <= accz_out_int;

data_ready <= '1';

END IF;

END PROCESS;

END Behavior;

Thanks everybody!

Altera_Forum · ‎06-21-2011

I don't think you can do arithmetic within a bit selection. Probably something more structured like having a combinatorial signal that gets (47 - count). (Of course count is std_logic_vector and 47 is not, so you'll need to figure that out, probably writing 47 in binary "101111"). Then you'll probably need a for-loop that checks each bit of count and assigns and compares to the value, and if they match assigns RXD to that accx bit.

I've also heard recommended to use numeric_std libraries, which are more of a standard, instead of signed/unsigned/etc.(which are from Synopsys, although pretty much everyone understands them. I just think numeric_std does a better job of conversions operator overloading, although not positive).

Altera_Forum · ‎06-21-2011

The index arithmetic like accx_out_int(47 - count) can work, if count is of the integer type. With the legacy non-IEEE libraries, conv_integer() should be the right type cast.