I am working in 8 bit pixel values..for ease of coding i want to use conv_integer to convert this 8 bit std_logic_vector.is it cause any synthesise problem?is it reduce the speed of hardware...
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2 Answers
No, integers synthesise just fine. Don't use conv_integer though - that's from an old non-standard library.
You want to use ieee.numeric_std; and then to_integer(unsigned(some_vector));
If you still want to access the bits, and treat the vector as a number, then use the signed or unsigned type - they define vectors of bits (which can still have -, Z etc.) which behave as numbers, so you can write unsigned_vector <= unsigned_vector + 1.
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You will lose a lot of the functionality that comes with the standard logic vector such as having the value 'Z' or 'X'. If you need access to the bits leave it as std_logic_vector, or cast it to numeric_std. If you don't and you need to do some fancy arithmetic maybe it's better to have as an int. At the end of the day its all bits. Its normally best to keep to a vector type (std_logic_vector, unsigned, signed etc) at the top level so you can map each bit to a specific pin, but otherwise, you can use whatever types you want. Don't forget you are designing hardware now, not software, and there is a difference.
