address decoding in vhdl

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hello vizzie,

are selection lines the output data? and "00", "01" for example as addresses for the selection_lines??

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That's right. Selection lines is the output of the decoder. "00", "01" are the addresses from the hypothetical source; in this case your zpu processor.

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"00", "01" are the addresses which you will be decoding. The "0001", "0010" etc. are the output selection lines of the decoder.

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hello vizzie,

are selection lines the output data? and "00", "01" for example as addresses for the selection_lines??

hello,

in my attachment is my zpu_core(my processor) and a uart. mem_write is data output from my processor.it has 32 bits width.how to write an address decoder between zpu_core and uart serial?? i'm still thinking about it...any starting idea would be greatly appreciated..

Thx

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"00", "01" are the addresses which you will be decoding. The "0001", "0010" etc. are the output selection lines of the decoder.

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i still understand what you meant. the data output of my soft-core processor is 32 bits width. this data output will be passed to the input of uart. do i need address choices when only uart is connected to the processor and no other??

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which one is the address for the uart? 00 or 01 0r 10 or 11? should i fix the address of uart in my uart module?

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"00", "01" are the addresses which you will be decoding. The "0001", "0010" etc. are the output selection lines of the decoder.

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hello,

but to do the address decoding in vhdl, i dont have any idea how to write it..can someone guide me on how to do this ??

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It is very simple to write the VHDL code for an address decoder. A general code can be as follows:

2-to-4 address decoder: Using if-else construct

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if address = "00" then

selection_lines <= "0001";

elsif address = "01" then

selection_lines <= "0010";

elsif address = "10" then

selection_lines <= "0100";

else address = "11" then

selection_lines <= "1000";

end if;

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You can also use "case-select" and "when-else" constructs to code an address decoder.

You can use the higher address bus lines.

Example: If you use the a12 and a13 lines

cs=a12 and a13;

cs is the chip select signal for uart. In this case the base address is 0x3000