Hi,
Your post is not clear.
"char" is a variable type. It is just one byte, 8 buts wide. Often it us used to store text string data, which often are coded as ASCII.
"ASCII" is a coding style. It just says how to interprete the data.
Example:
"char" is like a sheet of paper. You may write numbers on it.
"ASCII" is how you interprete this number. Let's say you interprete it as a phone number.
Changing the size of the paper won't change the information, it still will show the same number (but you may be able to store numbers with different size/range). It surely can not change how you interprete the number. A phone number won't become a postal zip code.
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A char may contain a byte. It is 8 bits wide.
Lets say with bits "LHLL LLLH"
This is 0b01000001 (binary) = 0x41 (hex) = "A" (ASCII)
All already is the same, but differently interpreted. There is no need to transform anything.
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Just saying "a display" ..is not very informative.
There are many different
* types like LCD, LED, OLED
* types like dot matrix, fixed characters and symbols, 7 segment, 14 segment
* interfaces like parallel, I2C, SPI, raw
* sizes
* ....
***
When you talk about "function", "call", "program" it sounds like software. But VHDL is no software, it is not processed "instruction after instruction".
VHDL is hardware, where everything is processed in parallel.
Don't mix or compare it with software.
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Indeed you need to learn a lot. A forum can't replace school, nor can we replace reading books or viewing tutorial videos.
You need to learn to draw pictures, flow charts, timing diagrams.
Your task (indeed most tasks) basically are this style:
--> [black box] -->
Where:
--> (the left one) is the input. Interface, timing, bit width, named signals
[Black box] is the processing of data, maybe a lookup table, an algorithm, a formula...or combinations
--> (the right one) is the output. Interface, timing, bit width, named signals
Show what you have done so far, show drawings, pictures, give links to internet sources you use.
Show your solution, or at least parts of it. No need to be perfect.
.. then we all will help you to rectify mistakes and answer detailled questions
Klaus