[問]有關logic circuit的問題!!!

Pop^o

問題是用英文寫的...可以話,請幫忙翻譯翻譯...

Design a 4bit synchronous counter with a count sequence based on a number "6525".This number is our count sequence.

*注* Use a minimum number of J-K type flip-flops and NAND Gates in the design.Any appropriate logic minimisation technique can beused. Note that flip-flops have Q and Qbar outputs.

flyingfish

Pop^o网友,
找到一个不错的网站:
http://www.play-hookey.com/digital/ripple_counter.html
可看看counter的部分:basic 4-bit counter, synchronous binary counter, frequency
divider等..

有点印象,不知有没有记错:
(都还给老师了,现在也没有书参考)
1.先算要用几个4-bit counter
2. 用logic circuit,到了count 的数,要reset所有JK flip flop.
3. logic circuit部分,minimize gates的数目..(很懒,没去想,哈哈).

你作到那里了?
以前念书时好像用一本O'Malley的书,好像有讲到..

Synchronous circuit is driven by clock, and the flip flop will change state simultaneously in each clock cycle.4 bit meaning 4 jk ff, and you were asked to created the count sequence of

A0101
B1010
C1101
D0000

with 1 represent rising edge and 0 falling edge. Since the most significant bit is low all the time, you actually need only 3 jk ff. (8 is easier than 16)

The no. of Nand gate will be determined by your design technique ( k map etc).

You can start with a state diagram, followed by state assignment, state table, transistion table and  excitation table.

Pop^o

clearskies 于 3-6-2004 22:45  说 :
Synchronous circuit is driven by clock, and the flip flop will change state simultaneously in each clock cycle.4 bit meaning 4 jk ff, and you were asked to created the count sequence of

A0101
B ...

Thanks man....but how about the self restarting problem? for eg if the first starting number isnot in my conting sequence, how do i overcome the problem?
make assumption that all the non-counting sequnce number will go into my counting sequence?
or...?

flyingfish

哈哈,不好意思,原来我误解了Pop^o网友的题目,是"6-5-2-5"的sequence,不是6525个sequence..

看来我真的忘得7788了..

B=NOT(A),可以用第一个FF的Q和Qbar,用2个FF有没有问题?
if Q(FF1)=0101, Q(FF2)=0011,
C=Q(FF1) OR Q'(FF2)= (0101)OR(1100)=1101
这样可以吗?

麻烦网友教教我general method 里的transistion table and excitation table那
部分,我全忘了,又找不到书..
A        B             C       D
011 ->101 ->010 ->101

101又-->去011..
之后怎么作?

is it using the 7 LED decoder? i have forgotten the code.

Pop^o

calvin_tan 于 4-6-2004 07:05  说 :
is it using the 7 LED decoder? i have forgotten the code.

nono.....
dats is call BCD....this onw is counter with JK ff....
is different

flyingfish

记忆一点点恢复了..
好像是这样:

inputs to logic circuit先假设用3个FF吧)
Q(FF1)= 01010101
Q(FF2)= 00110011
Q(FF3)= 00001111
Outputs:
A=          01010101
B=          10101010
C=          11011101
D=          00000000

应该写成truth table的,这里从简写"横"的..
用Karnaugh map,可找出:
A=Q(FF1)
B=Qbar(FF1)
C=Q(FF1) OR Qbar(FF2)
所以不需FF3

好像不会有self restarting problem..

Pop^o

flyingfish 于 4-6-2004 23:41  说 :
记忆一点点恢复了..
好像是这样:

inputs to logic circuit先假设用3个FF吧)
Q(FF1)= 01010101
Q(FF2)= 00110011
Q(FF3)= 00001111
Outputs:
A=          01010101
B=          10101010
C=          ...

不是很明白Q(FF1)= 01010101
          Q(FF2)= 00110011
          Q(FF3)= 00001111
怎樣來的???

flyingfish

网友请参考
http://www.play-hookey.com/digital/synchronous_counter.html

Pop^o

明白了...謝謝各位....:>

use moore machine or mealee machine will save u a lot of time

Pop^o

我已經做到了...謝謝!!!!