# How to let a 7-segment BCD using negative edge-triggered flip-flops to repeat from 9 not F

#### Chris47

Joined Feb 7, 2021
7
Design a 7-segment displayed binary counter using negative edge-triggered flip-flops which counts between “ID number” and it’s “10’s complement value” in reverse order. It starts with complement value, decrements to your id number, then returns to complement value again, and repeats counting sequence with the applied clock signal.

This was my assignment, i solved it and everything is running correctly, but when the number is decreasing from the complement to my id number it repeats from F, however I need it to repeat from 9. How can İ solve this problem ?

#### ericgibbs

Joined Jan 29, 2010
18,059
hi Chris,
Welcome to AAC.
What is the ID number value.?
E

#### djsfantasi

Joined Apr 11, 2010
9,081
So you need to preset the flip flops to start counting down from 9?

#### Chris47

Joined Feb 7, 2021
7
So you need to preset the flip flops to start counting down from 9?
Yea so as you see the 7th BCD started from F, and the 8th was F and descended to C and it will continue. So I need it to descend from 9 not F

#### Chris47

Joined Feb 7, 2021
7
hi Chris,
Welcome to AAC.
What is the ID number value.?
E
The İD value is 19290096

#### ericgibbs

Joined Jan 29, 2010
18,059
Design a 7-segment displayed binary counter using negative edge-triggered flip-flops which counts between “ID number” and it’s “10’s complement value” in reverse order. It starts with complement value, decrements to your id number, then returns to complement value again, and repeats counting sequence with the applied clock signal.
hi Chris,
So you are using an 8 Stage Binary Counter, preloaded with
9181??14 and you need to count down to the 10's complement of
19290096
9181??14
then
9181??14
,,,, and keep repeating.

E

#### Chris47

Joined Feb 7, 2021
7
hi Chris,
So you are using an 8 Stage Binary Counter, preloaded with
19290096 and you need to count down to the 10's complement of
9181??14
then
19290096
,,,, and keep repeating.

E
The complement is 80709909, it is the complement to 9. Can it be complement to 10 ?

#### ericgibbs

Joined Jan 29, 2010
18,059
hi,
OK.
So you are using an 8 Stage Binary Counter, preloaded with
80709909 and you need to count down to the 9's complement of
19290096
then
80709909

#### Chris47

Joined Feb 7, 2021
7
hi,
OK.
So you are using an 8 Stage Binary Counter, preloaded with
80709909 and you need to count down to the 9's complement of
19290096
then
80709909
I think i solved the question wrong, it should be through the 10's complement but I solved it for the 9's complement. Or is it true ? Since in binary the maximum number is 9 ?

#### ericgibbs

Joined Jan 29, 2010
18,059
hi Chris,
If you are using 8 Bit BINARY counters, you will need very complex decoding logic, if you are counting to decode DECIMAL values.
when using an 8 Stage counter.

Since in binary the maximum number is 9 ?

No, it is 15 == Bits 1111 or 'F'

I would advise you confirm if it is Binary or Decimal

E

#### Chris47

Joined Feb 7, 2021
7
hi Chris,
If you are using 8 Bit BINARY counters, you will need very complex decoding logic, if you are counting to decode DECIMAL values.
when using an 8 Stage counter.

Since in binary the maximum number is 9 ?

No, it is 15 == Bits 1111 or 'F'

I would advise you confirm if it is Binary or Decimal

E
It is binary, but now i have a problem how will I do it for the 10's complement

#### ericgibbs

Joined Jan 29, 2010
18,059

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#### Chris47

Joined Feb 7, 2021
7

#### ericgibbs

Joined Jan 29, 2010
18,059
Design a 7-segment displayed binary counter using negative edge-triggered flip-flops
hi,
Checking you original circuit image, they are positive edge clocked bistables not negative edge trigger.