89Views3Replies

Author Options:

decoder ? Answered

Hello ,
I  am going to make  decoder  for micro controller ,   I want to know how does decoder make for  microcontroller
I have 4 registers
I =Instruction Register
A= Address register
R1= register R1
R2 =register R2

Logic 0= deactivate
Logic 1= activate

I     A   R1    R2        out
1   1    1         0            1     //  mov R1
1   1    0          1           1     // mov R2

I AR1R2        out
0000                 0000000000000001
0001                 0000000000000010
0010              0000000000000100
0011              0000000000001000
0100             0000000000010000
0101             0000000000100000 
0110             0000000001000000 
0111            0000000010000000 
1000            0000000100000000
  1001             0000001000000000
1010             0000010000000000
1011            0000100000000000
1100            0001000000000000
1101            0010000000000000
1110            0100000000000000
1111           1000000000000000

If I know input than how to know what will decode ?

Tags:digital

Discussions

0
None
iceng

4 years ago

You need more then 4 bits to decode more then 16 things.

5 bits can decode to 32 things,

6 bits can get you a cup of java or decode 64 things.

etc, etc..

0
None
veadiceng

Answer 4 years ago

can you tell me which decoder is used for 8051 microcontroller ?

0
None
icengvead

Answer 4 years ago

Dear decoder;

You never give a best answer to anyone (like me) who helps you !!

.

Do you know binary arithmetic and the base two series which would really open your mind in these endless decoder questionable questions.

Sure the 8051 is 8bits and decodes to 256 possible instructions BUT it can use some16bit instructions that could decode to over 65 thousand but they don't use them all.

.

Back in the day a guy got a rich ideas of patenting every combination of binary arrangement of bits in a 32k EEPROM you can wont believe what really happened next..

.

Ford who made the model T car once offered to pay a worker by putting a penny first-day one on a checker board square and two pennies on the second day on the next square and four pennies the third day on the next square until the board is full.

What would you think the assembly worker should have done ??

0
None
veadiceng

Answer 4 years ago

I always respect you don't think wrong about me

may be its my language problem

ok look following things

4bits can decode 16 things.
5 bits can decode to 32 things,
6 bits can decode 64 things.
8 bit can decode 256 things
16 bit can decode 65536 things
etc, etc..

suppose I am using 16 bit input
,ram_rd_sel ,ram_wr_sel ,src_sel1 src_sel2,alu_op,wr ,psw_set ,cy_sel ,pc_wr ,pc_sel ,imm_sel ,src_sel3 ,comp_sel ,bit_addr ;,rom_addr_sel ,ext_addr_sel

16 bits can represent 65536 states example nop, mov , movc, add addc ........upto 65536
when all input will 0 then perform nop state
as same we can decode different state at different input

I am not sure that I am going to correct way . ?

0
None
icengvead

Answer 4 years ago

Excellent !

You know the powers of two and the 8051 instruction set

http://www.win.tue.nl/~aeb/comp/8051/set8051.html

A good first exercise is to send a "Hello World" text message.

I used to program 8051 when I was young back then you needed to hang i/o chips eeprom, clock etc outside.

Now the 8051 is low cost, Atmel produces a variety of multipin devices with all that hardware included inside.

Do you want to use one ?

0
None
rickharris

4 years ago

Your question makes no sense. We need a LOT more information.

0
None
veadrickharris

Answer 4 years ago

ok suppose I am using 3-8 decoder

4 bits used for input. 16 bits for output.

that means I can decode 16 different things as I mention in table

but I want to decode more then 16 things , how to do ?