mod 5 down counter

Thread Starter

bhuvanesh

Joined Aug 10, 2013
268
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
 

ericgibbs

Joined Jan 29, 2010
18,872
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
 

JoeJester

Joined Apr 26, 2005
4,390
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.
 

ericgibbs

Joined Jan 29, 2010
18,872
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
 

Thread Starter

bhuvanesh

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

Thread Starter

bhuvanesh

Joined Aug 10, 2013
268
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

please help me to find where i am mistaking
 

ericgibbs

Joined Jan 29, 2010
18,872
now say whether my statement is right or wrong
1)no of states =mod number Yes
2)mod 5 so 5 states Yes
3)in up counter the counter resets itself at particular sequence to 0 Yes,..................and in down counter presets to 1 No.
It Presets itself to its Modulo value.

5) states so 3 f/f which are initally at 111 and sequence goes by 6543 again 76543, No
It would not start at 111, but be Preset at power up to the Modulo value
Post the full mod 5 sequence.
E
 

ericgibbs

Joined Jan 29, 2010
18,872
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
 

djsfantasi

Joined Apr 11, 2010
9,163
please show me mod 5 down counter.please
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.
 
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