What does X"46" represents in VHDL code ?

[shsshs]

I am new in Fpga. I am studing vhdl. I saw code like that

type CHAR_RAM_TYPE is array(0 to 39) of std_logic_vector(7 downto 0);

signal charRAM : CHAR_RAM_TYPE := ( 0=>x"41", 1=>x"6E", 2=>x"64", 3=>x"79", 4=>x"FE", 5=>x"47", 20=>x"31", 21=>x"34", 22=>x"2F", 23=>x"30", 24=>x"36", 25=>x"2F", 26=>x"30", 27=>x"37", others=>x"A0");

the thing that I want to ask is that does this representation X"46" mean "0 1 0 0 0 1 1 0" ? And does X show hegzadecimal?

thanks for help
moreover I want to help for lcd driver. I read some and am expecting leading information about lcd driver from your help. thnks.

 

[uoficowboy]

Re: help for fpga

I am new in Fpga. I am studing vhdl. I saw code like that

type CHAR_RAM_TYPE is array(0 to 39) of std_logic_vector(7 downto 0);

signal charRAM : CHAR_RAM_TYPE := ( 0=>x"41", 1=>x"6E", 2=>x"64", 3=>x"79", 4=>x"FE", 5=>x"47", 20=>x"31", 21=>x"34", 22=>x"2F", 23=>x"30", 24=>x"36", 25=>x"2F", 26=>x"30", 27=>x"37", others=>x"A0");

the thing that I want to ask is that does this representation X"46" mean "0 1 0 0 0 1 1 0" ? And does X show hegzadecimal?

thanks for help
moreover I want to help for lcd driver. I read some and am expecting leading information about lcd driver from your help. thnks.

Hi - yes the X means that the following numbers in the quotes are hexadecimal. Note that each digit represents exactly 4 bits. Section 4.d in this tutorial may be helpful for you.

However, can somebody clarify the way the initial assignment of that signal is being done? I have never seen it done that way. Does that simply mean that index 0 is assigned x41, index 1 is assigned x6E, so on and so forth and all indexes that aren't explicitly assigned are set to xA0?

 

[shsshs]

Re: help for fpga

when I synthesize the code it does not give any error. As a result of this I decide that this representation and assignment are correct.

 

[vipinlal]

Re: help for fpga

@uoficowboy: you are right. And about the initialization method used,this is a normal method of initializing arrays or vectors. The "others" key word is used to assign a value to all other bits or indexes the specified value.
For example,
signal x : std_logic_vector(3 downto 0) := (1 => '1', others => '0');
The initialized value in x is "0010".

I hope it is clear now.


--vipin
https://vhdlguru.blogspot.com/

 

[TrickyDicky]

Re: help for fpga

the thing that I want to ask is that does this representation X"46" mean "0 1 0 0 0 1 1 0" ? And does X show hegzadecimal?

Yes. X (or x) means it represents a hex string. You can also use B/b for binary:

s <= B"00101111";

or octal:

s <= O"8452";

there are also some neat things you can do using underscores to make it more readable:

s <= B"0010_1111";
s <= X"0A_8F_77_FF";

Also, for integers, you can create literals in any base using # (in the range 2-16):

my_int <= 16#AAF0#; --literal AAF0 in base 16
my_int <= 2#1101#; --literal 13
my_int <= 14#AA654#; --you do the math

 

[Umair_ali]

Re: help for fpga

if you are new to FPGA... try verilog... its less wordy and easy.... but its my opinion and i am not trying to offend any one

 

[shsshs]

Re: help for fpga

thanks for all helps. I understand clearly

I know little bit verilog from my univercity but in my internship , I am responsible to learn and apply on fpga with vhdl... But I have been using fpga for two weeks and I think it is funny and easy... my fpga is spartan 3 AN -XC3S700AN. there is a lot of facility to learn I have used rs232 and vga. and I am stilll working on vga it is funny