# Hex and BCD puzzle (to me anyway)

Joined Jul 31, 2013
222
I'm looking to buy an (old) UNILAB counter module of amazon (unilab counter module 120) with a view to using it in a project - and saving me a little construction. But I can see from the picture in the ad that there is a CD4510BE BCD up/down counter, feeding a MC14495 which is a hex decoder driver. Both description obtained from Googling data sheets.
My question is why is the dec/driver not a BCD type and how can the 4510 and 14495 work together..or am I missing something ?

#### AlbertHall

Joined Jun 4, 2014
12,023
The '14495 takes four binary digits, interprets them as hexadecimal, and drives a single seven segment display.
If you feed those four inputs with the four bits of a BCD digit then the display will correctly follow the BCD digit.

#### dl324

Joined Mar 30, 2015
14,462
My question is why is the dec/driver not a BCD type and how can the 4510 and 14495 work together..or am I missing something ?
BCD [0123456789] is a subset of hexadecimal [0123456789ABCDEF].

Joined Jul 31, 2013
222
Thanks..I made incorrect assumptions about what hex actually was. I'm pretty sketchy about logic ! Does that mean if I swapped out the 4510 for a 4516 I could count to F ?

#### dl324

Joined Mar 30, 2015
14,462
I'm pretty sketchy about logic !
It's a different numbering system (decimal vs. hexadecimal), not logic. Digital logic is based on 1's and 0's. We can think of groupings of 1's and 0's as binary, octal, decimal, or hexadecimal. We call a single 1/0 a bit, 4 bits is a nibble, 8 bits is a byte, etc.
Does that mean if I swapped out the 4510 for a 4516 I could count to F ?
Yes.

EDIT: corrected 0's, some were o's.

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#### AlbertHall

Joined Jun 4, 2014
12,023
Does that mean if I swapped out the 4510 for a 4516 I could count to F ?
If the counter is just a single digit then, yes, you can.

#### crutschow

Joined Mar 14, 2008
29,791
If the counter is just a single digit then, yes, you can.
Why the limit to one digit?

#### AlbertHall

Joined Jun 4, 2014
12,023
Why the limit to one digit?
I was thinking that the carry would be wrong for the subsequent digit, but of course it wouldn't be.

Joined Jul 31, 2013
222
Thank you for all the helpful replies..The unit is only a fiver.. It does only have a single 7 segment display but will serve my project quite well with minimum mods. I have now googled the Hex sequence and am a little wiser..I'll go ahead and order one..