# mod 5 down counter

Discussion in 'Homework Help' started by bhuvanesh, Sep 20, 2014.

1. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
in mod 5 down counter at 5th clock pulse whether circuit resets to 000 or 111?

2. ### crutschow Expert

Mar 14, 2008
16,217
4,336
Go through the count sequence. That will tell you what it should do at the 5th clock pulse.

3. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
At fifth clock pulse it resets to 000 then at 6th pulse it become 111 and 7th it gives 110 and and in 11th it resets.Consider 6th as 1st pulse (coz counter rest,just for sake of clearance )
now the counter resets on 6th pulse.MOD 5 counter is called so since it resets at fifth clock pulse.Now it looks like violating the rule.do u get my point?Thanks

4. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,245
565
A modulo 6 down counter should not be 111 at the 6th pulse.
If its wired as a modulo 6 down counter it should continue to be a modulo 6 down counter, not revert to a different modulo value.

E

bhuvanesh likes this.
5. ### JoeJester AAC Fanatic!

Apr 26, 2005
3,663
1,530
modulo X counters count from 0 to X-1 in the up position. The reset logic will reset the counter to zero.

Modulo X counters count from X-1 to 0 in the down position. The preset logic will preset the counter to X-1.

bhuvanesh likes this.
6. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
thanks thats the magic word i forget presets.thanks

7. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
mod 5 counter presets at 5th clock pulse and mod 6 counter presets at 6th clock pulse, am i right?

8. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,245
565
Consider an Up counter, what Modulus do you make the following sequence.?
[Remember the binary value change occurs at a Clock Edge, it can be either a rising or falling edge, depends upon the bistable design].

You say: mod 5 counter presets at 5th clock pulse and mod 6 counter presets at 6th clock pulse,
Post what your binary values would be for a mod 5 Down counter.
E

000 = 0 > initial state
1 clk
001 = 1 > after 1st clk
2 clk
010= 2 > after 2nd clk
3 clk
011= 3 > after 3rd clk
4 clk
100= 4 > after 4th clk
5 clk
101 = 5 > after 5th clk
6 clk
000 = 0 > after 6th clk
7 clk
110 = 1

bhuvanesh likes this.
9. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
At 5th clock pulse the binary value 101 make the combimational circuit to reset the counter asynchronously (independent of clock pulse)

10. ### MrChips Moderator

Oct 2, 2009
14,291
4,197
A mod-5 up-counter counts from 0 to 4.

101 is not a valid state.

11. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
yes at 5th clock pulse counter resets to 000 ,right?

12. ### MrChips Moderator

Oct 2, 2009
14,291
4,197
For a mod-5 down-counter, the count sequence is

4-3-2-1-0-4-3-2-1-0-4-3....

13. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
now say whether my statement is right or wrong
1)no of states =mod number
2)mod 5 so 5 states
3)in up counter the counter resets itself at particular sequence to 0 and in down counter presets to 1
5) states so 3 f/f which are initally at 111 and sequence goes by 6543 again 76543

the counter restes (0) pt preset(1) but according to your statement its changing to 001(4).how is that possible

14. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,245
565
Post the full mod 5 sequence.
E

15. ### MrChips Moderator

Oct 2, 2009
14,291
4,197
5, 6, 7 are not valid states in a mod-5 counter.

Hence don't preset your counter to 7.

16. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
please show me mod 5 down counter.please

Apr 5, 2008
16,983
2,965
18. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,245
565
hi ,
I think whats confusing you is that you are always assuming a Reset at the end of the modulo count.
Most logic bi-stables can be Reset to Qout Low [ '0'] but also they can be Preset to Qout High [1].

An Up counter would be Reset to '0' when its modulo count is exceeded.
eg: 000,001 ,,,, 011, 101, 000
A Down counter would be Preset to its modulo value when it 'tries' to count below zero [0].
eg: 101,100,,,,,, 001, 000, 101

19. ### djsfantasi AAC Fanatic!

Apr 11, 2010
3,486
1,245
This is Homework Help, not Homework Done for You. Show what you have done so far.
I've noted 3-4 posts that show the modulus 5 count down sequence, and here it is again:
4-3-2-1-0-4-3-2-1-0-4-3-2…
If you study and understand this sequence, many of your questions will be answered.

20. ### bhuvanesh Thread Starter Member

Aug 10, 2013
268
2
i google as mod 5 down counter .i didnt get that .could u suggest me any good link to see mod N down counter