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**posted on**

October 1, 2007, 6:07 am

this is probably easy to do but i cant think how at the moment.

how could i take an 8 bit number in a file and break it down into the 100s

10s and 1s and

put the results into three other files so for example if i had 11001011

which is 203, how can i

put 2 in the hundreds file, 0 in the tens and 3 in the units file.

would this be done best in a lookup table?

thanks in advance for any advice

Hayley

Re: help breaking down number inti 100s 10, 1s

On Mon, 01 Oct 2007 06:07:06 GMT, "Hayley"

Hmm, can you elaborate? What would this be used for (I smell homework

:-), and how exactly are your files encoded - is this "11001011" a

byte, or 8 bytes (e.g. 31 31 30 30 31 30 31 31)? How should the

resulting files be encoded?

I don't think so, unless you have 768 bytes to spare and need to

compute this really fast - since there apparently are files involved,

the file system operations will use most of the time anyway.

I'd do it like this:

- Divide the value (assuming you already have it "verbatim" and not as

"text") by ten. Keep the integer division result and the remainder.

- write the remainder into the current file (the first time you do

this, it'll be the units file, then the tens, then the hundreds)

- for the next file, repeat the above with the division result as the

new number.

(Another way to do it, if your micro does not have division, would be

to subtract 100 until you end up with a value below 100, and count how

often you can to do that. Repeat with 10 and 1 keeping the final

result of the previous steps. The files are written to in the reverse

order in this case.)

Regards,

Gilles.

Re: help breaking down number inti 100s 10, 1s

Hi thanks for the replies,

this is a home project for a telescope, im making a device that counts

the number of times the focus knob is turned and then displayed

on 3x 7 segment displays that was why i needed the binary counting

number broken down into the 100s 10s and 1s so they can be sent to the

correct

display segment. the focus knob is geared down and motorised you have the

turn it

many times for just a slight adjustment so to keep track of different focal

points

i want to put a counter on it. i can put the number in the EEdata so it wont

be lost

during powerdown.

Re: help breaking down number inti 100s 10, 1s

Hi Haley,

Interesting project and apologies for the "assignment assumption" :-)

the

focal

The "files" had me confused, where do they come in? I'd store the

current focus setting in the EEdata as a single byte (in case that is

the persistent "file" storage), converting to three digits for 7

segment display only as needed. (on the fly)

What programming language are you using? If C, something along the

following lines would compute the values to output to the 7 segment

decoders given an 8 bit unsigned number:

void DisplayValue(unsigned char number, unsigned char digits)

{

unsigned char currentSegment;

for(currentSegment = 0; currentSegment < digits; currentSegment++)

{

SetSegmentValue(currentSegment, number % 10);

number /= 10;

}

}

You would pass 3 for "digits" in this case. (the maximum that makes

sense with 8 bit integers. You could also make the currently hardcoded

"10" a into a "base" parameter, and alternatively pass 16 to show

values in hex - assuming your digit decoding mechanism/hardware

supports it)

"void SetSegmentValue(unsigned char segment, unsigned char value)"

is a hardware-specific routine you must provide that sets a segment

given by number (starting with 0 at the right) to a certain value (0-9

resp. 0-15)

Regards,

Gilles.

P.S.: Caution: untested code ...

Re: help breaking down number inti 100s 10, 1s

Hi,

I am using assembler with a pic 16f84, my idea was to

have a register address with the focus count position in it.

which is incremented or decremented accordingly.

the bit i am stuck on is when i want to send the 3 digit number to the

outside world

to some 7 segment displays i need to convert the binary number into the 100s

10s and 1s.

I am ok with the input to the pic, counting, driving the display, its just

the breaking down the number

i am stuck with

thanks for your reply

Re: help breaking down number inti 100s 10, 1s

Hi Haley,

On Tue, 02 Oct 2007 15:34:22 GMT, "Hayley"

I'm not familiar with that chip unfortunately, and its been some time

I did assembly (6502, 6809, 8080, Z80, 68000, you can probably tell

how long its been).

Had a quick glance at the datasheet - no division instruction, so

method number 2 (subtract 100 as long as value is larger than 100,

keep track of how many times that worked, this is digit 2, repeat same

principle for 10 and 1 yielding digits 1 and 0 respectively) could

work.

In pseudo-assembler:

reserve three registers or memory locations for the 100s, 10s and 1s

values. An additional tempory location (maybe that weird "W" register

that seems to play the role of a "wrong side of the equation

accumulator" :-) is needed for computation.

"Code" for the first (leftmost) digit

clear register for 100s digit

loop100: subtract 100 from current value

if result is negative jump to done100

increment register for the 100s digit

goto loop100

done100: add 100 to current value

(to recover the value before it got negative,

may need to clear carry here before proceeding)

repeat code above for loop10/done10 and loop1/done1 accordingly.

You should end up with the 3 7 seg values in the three registers.

Hope this helps / makes sense / actually works, good luck!

Regards,

Gilles.

Re: help breaking down number inti 100s 10, 1s

You should have just said this to begin with. ;-) To use the following

code, just put your binary value into binX, binU, binH, and binL. Then

"call binary

___to___bcd". The output will be stored as two BCD digits per byte.

To turn the values into ASCII, you can simply "addlw 0x30" for each 4-bit

BCD value. This code treats the 32-bit input as unsigned.

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;

; Variables for binary to BCD conversion

;

count

temp

; 32 bit binary value

binX

binU

binH

binL

; 10 digit BCD conversion output

billions

___and___hundredmillions

tenmillions

___and___millions

hundredthousands

___and___tenthousands

thousands

___and___hundreds

tens

___and___ones

;

; binary

___to___bcd - convert 32bit unsigned binary value to 10 digits of BCD

;

binary

___to___bcd

bcf STATUS, 0 ; clear the carry bit

movlw .32

movwf count

clrf billions

___and___hundredmillions

clrf tenmillions

___and___millions

clrf hundredthousands

___and___tenthousands

clrf thousands

___and___hundreds

clrf tens

___and___ones

loop32

rlf binL, F

rlf binH, F

rlf binU, F

rlf binX, F

rlf tens

___and___ones, F

rlf thousands

___and___hundreds, F

rlf hundredthousands

___and___tenthousands, F

rlf tenmillions

___and___millions, F

rlf billions

___and___hundredmillions, F

;

decfsz count, F

goto adjDEC

RETLW 0

;

adjDEC

bcf STATUS, IRP

movlw tens

___and___ones

movwf FSR

call adjBCD

;

movlw thousands

___and___hundreds

movwf FSR

call adjBCD

;

movlw hundredthousands

___and___tenthousands

movwf FSR

call adjBCD

movlw tenmillions

___and___millions

movwf FSR

call adjBCD

movlw billions

___and___hundredmillions

movwf FSR

call adjBCD

;

goto loop32

;

adjBCD

movlw 3

addwf INDF,W

movwf temp

btfsc temp,3 ; test if result > 7

movwf INDF

movlw 0x30

addwf INDF,W

movwf temp

btfsc temp,7 ; test if result > 7

movwf INDF ; save as MSD

RETLW 0

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