# Binary to decimal: how to send 8 bits to 2 displays or ...?

Discussion in 'Misc Electronics' started by Tari, Aug 25, 2003.

1. ### TariGuest

Hello!

I'm working on a project that requires to display binary words (8
bits) on a 7-segment display. It is the purpose to show those words
decimally. Anyone knows of a device that can convert an 8 bit word
into the correspondent decimal numbers (0, 1, 2, ..., 9, 10, ..., 64
(that's where I have to set a reset))?
I was thinking of using 2 displays, but I don't know how to deal with
it. Or does there exists a 7-segment-display that exists of 2 parts,
so that you automatically can show numbers like 20 etc. ?

I hope some one can help me.

Greetings
Tari

2. ### Richard HoskingGuest

Tari
It might be easiest to represent the 8 bit word as a 2 digit Hexadecimal
number. If you *must* represent it as a decimal, it will take three digits
(000-255) and some significant logic to convert from binary to decimal. The
simplest way I can think of to do this would be to use a microcontroller
which could also drive the display. Is this a possibility?

Richard

3. ### Fred AbseGuest

Quick and dirty method for a one-off:

State table in 16-bit EPROM, or two 8-bit EPROMS. Drive the address lines
with the input byte and use the data lines (buffered) to drive two
7-segment displays.

Breadboard it in an hour. Write the state table in ten minutes.

Use those 4716s you never could bring yourself to throw away

Otherwise you could use a couple of 74*185 binary to BCD converters,
then two 74*49 BDC to 7-segment decoder/drivers driving two 7-segment
displays.

There's lots of other ways of doing it, but since it looks like a school
project, I'll leave you to find those out yourself.

4. ### Tony WilliamsGuest

Set a reset? Sounds like you might be coming from a counter.
If so don't use a binary counter, use a 2-digit BCD counter.
Each digit then goes directly to a BCD-7segment display/driver.

If it has to be a binary input then the old microprocesser
logic would be..... Split the binary D7-D0 into two nibbles,
D7-D4 is hi-nib and D3-D0 is lo-nib. Look at lo-nib.

If lo-nib is less than 9, then the two BCD output digits are
simply hi-nib and lo-nib. If lo-nib is greater than 9, then
the two BCD output digits are (hi-nib + 1) and (lo-nib + 6).

This could be done in hardware (1x 4-bit magnitude comparator,
and 2x 4-bit adders), or in software in a microprocessor.
A little 18-pin PIC has just about enough i/o to do it.