Magnitude Comparators

[Michael]

Hi,

I'm working on a school project where I need to compare 16bits (4 BCD
values) from a CMOS logic system and need alternative ways of doing it.

So far I've got 4 cascaded 4063 bit comparators, ADC conversion but I'm
struggling for a third. Can anyone suggest a method?

I was thinking about using a CMOS compatible 74 series bit comparator but
it's not really that different from the 4063 method......

Cheers,

Michael

 

[Stephen J. Rush]

On Fri, 07 Dec 2007 10:40:15 +0000, Michael wrote:

Hi,

I'm working on a school project where I need to compare 16bits (4 BCD
values) from a CMOS logic system and need alternative ways of doing it.

So far I've got 4 cascaded 4063 bit comparators, ADC conversion but I'm
struggling for a third. Can anyone suggest a method?

I was thinking about using a CMOS compatible 74 series bit comparator
but it's not really that different from the 4063 method......

A microcontroller running a short loop? Some of the Atmel 8-bit
microcontrollers are absurdly cheap.

 

[Chris]

On Dec 7, 4:40 am, "Michael" <mQiQcQhQaQe...@QmQhQiQmQsQ.QcQoQ.QuQkQ>
wrote:

Hi,

I'm working on a school project where I need to compare 16bits (4 BCD
values) from a CMOS logic system and need alternative ways of doing it.

So far I've got 4 cascaded 4063 bit comparators, ADC conversion but I'm
struggling for a third. Can anyone suggest a method?

I was thinking about using a CMOS compatible 74 series bit comparator but
it's not really that different from the 4063 method......

Cheers,

Michael

Hi, Michael. You might get some homework points for variety by
latching the two 16-bit numbers into shift registers, then serially
comparing the bits, starting with the most significant. First non-
equal (discrete logic here) sets the greater-than or less than flip-
flop. which locks the other one out. Both flip flops reset on the
latch signal.

If it were an 8 X 8 or even a 12 X 12 compare you could use one PROM.
You might offer a suggestion that you could compare the first byte
using a PROM, then if equal, compare the second byte using the same
PROM or a second PROM if you want to stay away from latching and
sequential logic.

Someone else has mentioned using a PIC, which is a valid one-chip
solution.

Not too many ways to compare two numbers except to compare them, I
guess.

Good luck
Chris