Encoder

1
?????? ??????? ?????? ?????????
????? ???, ??? ?????????????????? ?? ????

• ????? ?? ?????? ??
• ???? ?????, ??????????? ?????? ?"?

2
Encoder

• Encoder encodes bitstream or other signal or data
  into a form that is acceptable for transmission
  or storage.
• A decoder does the reverse
• Endec does both
• Codec does both as well but in software

3
Examples

• A modem is an endec
• A program that creates a compressed version of
  music or video, say MPEG is a codec
• MIME to send binary files over text email
• PGP to send encrypted messages

4
?????? ??????? ?????? ?????????
????? Decoder

• n ?????? ??????? ???? ?????? ????? 02n-1

• 2n ?????? ???? ????? i ???? "1" ??"? ?????? ??
  ??? i.

(??????)
(?????)
??? ??? ??? ??? ??? ???
A1 A0 D3 D2 D1 D0
0 0 0 0 0 1
0 1 0 0 1 0
1 0 0 1 0 0
1 1 1 0 0 0
5
?????? ??????? ?????? ?????????
??????? Decoders

• ???? n ?????? ??????.

• ???? 2n ?????? ??????.

?????? ??? ???? ?? ?????? ???? ? minterm
?????? ? ???? ??? 1 ??? ??? ? minterms ???
0. ????? ???? ?????? ?????? ??????.
6
?????? ??????? ?????? ?????????
??????? Decoders

• ???? n ?????? ??????.

• ???? 2n ?????? ??????.

?????? ??? ???? ?? ?????? ???? ? minterm
?????? ? ???? ??? 1 ??? ??? ? minterms ???
0. ????? ???? ?????? ?????? ??????.
ENABLE
7
?????? ????????

• ??????? ?????? ????? ??????? (????? ?????
• NAND ????? AND).

• ???? ?? Enable ??? "?????" ?? "????" ?? ??
  ?????.

E A1 A0 D0 D1 D2 D3
0 0 0 0 1 1 1
0 0 1 1 0 1 1
0 1 0 1 1 0 1
0 1 1 1 1 1 0
1 ? ? 1 1 1 1
???? ???? ???? ???? NAND ? Enable ????? ?"? ???
"0".
8
???? ? Enable
(Enable ?????)
???? Decoder n?2n ?"? ??? n-1?2n-1, ?????? ???
Enable

• ???? Z0 ????? ?-Decoder ?????? ???? ???? ?"? xy
  ?? ?????? ??????? ????? 1.
• ????? ?? ?-Decoder ?????? ????? ?????.
• ?????? ????? (????? ????? 4 ?????) ???? Z1.

9
????? ???? ?????? ?"? Decoders

• ?"? ????? OR ?? ??????? ???????? ???? ???? ?????
  ??????.
• ?????? ??? ??????? ???? ?????? ?-Decoder ????
  ???? ???? ???????? ??? ?"? Decoder ????.

????? ????? FA ?"? Decoder.
00 01 11 10
0 0 1 0 1
1 1 0 1 0
00 01 11 10
0 1
1 1 1 1
10
????? FA ?"? 3?8 ????
2 ? 4
0
a
20
1
b
21
2
C
3
E
a
20
b
21
E
11
????? ?????? ??????
MSB
LSB
00 01 11 10
0 1 1 1 0
1 1 1 0 1
A B C f
0 0 0 0 1
1 0 0 1 1
2 0 1 0 0
3 0 1 1 1
4 1 0 0 1
5 1 0 1 1
6 1 1 0 1
7 1 1 1 0
A
12
????? ???? ????
???? ?? ??? ???????
B A C f
0 0 0 0 1
1 0 0 1 1
2 0 1 0 1
3 0 1 1 1
4 1 0 0 0
5 1 0 1 1
6 1 1 0 1
7 1 1 1 0
00 01 11 10
0 1 1 1 1
1 0 1 0 1
B
13
????? ???? ????
???? ?? ??? ???????
B A C f
0 0 0 0 1
1 0 0 1 1
2 0 1 0 1
3 0 1 1 1
4 1 0 0 0
5 1 0 1 1
6 1 1 0 1
7 1 1 1 0
00 01 11 10
0 1 1 1 1
1 0 1 0 1
B
14
??????? - Encoders

• ???? ??????? "?????" ??????
• 2n ??? ?????.
• n ??? ?????.

D0
A0
Encoder
D1
4?2
D2
A1
D3
??? ??? ??? ??? ??? ??? ???
D3 D2 D1 D0 A1 A0
0 0 0 1 0 0 ?0
0 0 1 0 0 1 ?1
0 1 0 0 1 0 ?2
1 0 0 0 1 1 ?3

• ??? ????? "??????" ???? ?????? ????? ?? ?? ??????.

????? "????" ???? ?? ??????
15
????? ???????
D0
D1 D3
D1
A0
D2
D2 D3
A1
D3

• ?? D0 ???? "?????".
• ?????? ??? ???? ????? ?"? ???? OR ???? ??? ??
  "??????" ?? ?????? ??? ?? ???? ? ???? ??????
  ???????? ??????? ??????? ????.

????? ???????? Priority Encoder

• 2n ??????.
• n ?????? ????? Valid.

???? "??????" ????.
16
????? ???????? Priority Encoder

• ???? ????? ?? ???? ?????? (MSB) ????? "1".

D3 D2 D1 D0 A1 A0 V
0 0 0 0 0 0 0
0 0 0 1 0 0 1 0
0 0 1 ? 0 1 1 1
0 1 ? ? 1 0 1 2
1 ? ? ? 1 1 1 3
not valid
Valid
D1
D1
1 1

1 1 1 1
1 1 1 1

1 1 1 1
1 1 1 1
1 1 1 1
D2
D2
D3
D3
D0
D0
A1 D2 D3
A0 D3 D1D2
V D0 D1 D2 D3
D3
A0
D2
A1
D1
V
D0
17
?????? Multiplexer
????? ????? ???? ?? ?? ?????? ???? ??????? ????
??? ???? ?? ????? ?? ??????. ???? ????? ???? ??
???? ???? ??? ????? ?????? ?? ????? ??????? ?? ??
????? ????.

• 2n ??? ?????.
• n ??? ????? / ????? / ?????.
• ?? ????? ????.

MUX 4?1
I0
Y
I1
I2
I3
S1
S0
18
?????? Multiplexer
????? ????? ???? ?? ?? ?????? ???? ??????? ????
??? ???? ?? ????? ?? ??????. ???? ????? ???? ??
???? ???? ??? ????? ?????? ?? ????? ??????? ?? ??
????? ????.

• 2n ??? ?????.
• n ??? ????? / ????? / ?????.
• ?? ????? ????.

MUX 4?1
I0
Y
I1
I2
I3
S1
S0
19
????? ????
I0
S0
S1
I1
I2
I3

• ????? ???????? ??????? ?? Enable (?????).
• ???? ????? ??? ?????? ?? ????.

???? ????????
E S Output
0 ? All Os
1 0 Select
1 1 Select
20
????? ???????? ????????? ?"? ??????
???? "?????" ???? ??????? ???? n ?????? ?????
????? ??? n ?????? ????. ???? ???????? ?????
??????. ???? 1 ?????? ??????? ?????? ??? ??????
????? ? "0" ????.
?????
FA BC
A B C F
0 0 0 1 0
0 0 1 1 1
0 1 0 1 2
0 1 1 1 3
1 0 0 0 4
1 0 1 0 5
1 1 0 0 6
1 1 1 1 7
1
21
???? "???????"

• ????? ????? ???????? ??? ???? ????? ?????
  ??????.
• ????? ???????? n-1 1

????
?????
A B C F
0 0 0 1
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 0
1 0 1 0
1 1 0 0
1 1 1 1
22
???? "???????"

• ????? ????? ???????? ??? ??? ????? ???? ??????.
• ????? ???????? n-1 1

????
?????
A B C F
0 0 0 1
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 0
1 0 1 0
1 1 0 0
1 1 1 1
23
????? ????? 2 ???? 2 ?????
A B C D F
0 0 0 0 0
0 0 0 1 0
0 0 1 0 0
0 0 1 1 1
0 1 0 0 0
0 1 0 1 1
0 1 1 0 1
0 1 1 1 0
1 0 0 0 1
1 0 0 1 1
1 0 1 0 1
1 0 1 1 0
1 1 0 0 1
1 1 0 1 0
1 1 1 0 0
1 1 1 1 1
CD
CÅD
CD
(CÅD)
C
CD
0
CÅD
1
f
CD
Y
2
D
s1
s0
3
(CÅD)
A
B