HC11 convert BCD to binary

windozeuser · Oct 4, 2010

I have an array (4 byte) with each byte being a possible BCD digit 0 to 9

How can I convert this entire byte BCD array into a 16 bit binary number?

I'm treating the entire array as one number, so array+3 = thousands, array+2 = hundreds, array+1 = tens, array = units

ericgibbs · Oct 4, 2010

Look here.
https://www.electro-tech-online.com/threads/convert-bcd-to-binary.41808/

windozeuser · Oct 4, 2010

Yeah I've been reading it over and over, I can't figure out how to write it for the HC11 in assembly tho

Wp100 · Oct 4, 2010

Hi,

Tried here ..?

Pommie · Oct 4, 2010

windozeuser said:
Yeah I've been reading it over and over, I can't figure out how to write it for the HC11 in assembly tho

The problem is that that chip is over 25 years old (and based on the older 6800) and, I guess, no one here has used it. I did program the 6809 at one time but it's too long ago to remember.

Mike.

windozeuser · Oct 4, 2010

Code:

******************************************************************
; Set up the Pincode buffer to store the code the user enteres from keypad

  ORG 0 ; Store Pincode in RAM
Pincode   RMB   4   ; Pincode 4 byte buffer

******************************************************************
*	<<< MAIN PROGRAM LOOP >>>
******************************************************************
	ORG	PROG
START

	; Load the Pincode array with the value 1234, with each digit being in it's own byte of the array  
  ldaa #1
  staa Pincode
  ldaa #2
  staa Pincode+1
  ldaa #3
  staa Pincode+2
  ldaa #4
  staa Pincode+3




*******************************************************************
*CONVERT BCD TO A the 16bit binary decimal NUMBER
*******************************************************************

BCDBIN 	  

        
  clra
  clrb ; clears D
  std BINVAL ; Clear BINVAL 
  
thousands
  
  tst Pincode
  beq hundrends
  addd #1000
  dec Pincode
  bne thousands
  
hundrends
  
  tst Pincode+1
  beq tens
  addd #100
  dec Pincode+1
  bne hundrends

tens
  
  tst Pincode+2
  beq processpin
  addd #10
  dec Pincode+2
  bne tens

processpin

; take care of units
  
  addd Pincode+3
  
  std BINVAL ; BINVAL now equal to 16bit binary equiv

	ldx BINVAL
	
	cpx SECRET
	
	beq SUCCESS
	
	
	swi		;end program 

SUCCESS            
	
	ldx	#msg11	;point X to  message ; Display you got the Pin correct!!!

	jsr	OUTSTRG	;output it

This is the code I took from my larger program, basically I am polling a 4x4 keypad and storing a 4 digit "Pin number" the user enters into an array. The problem is each digit is in a separate byte of the array, and I need to convert the entire array into the 16 bit BCD equivalent.

This converts 1234 into 0x08D2, which is wrong, it should be 0x02D2, I can't figure out whats wrong!

Any help would be greatly appreciated!

Pommie · Oct 4, 2010

I can't see anything wrong with your code but I did notice that 1234 is 0x04D2.

Mike.

windozeuser · Oct 4, 2010

I found the problem with the help of the trace command and selecting 0 for all values,

; take care of units

addd Pincode+3

This is adding the address to the D register rather than the value at the address, I tried doing intermediate #Pincode+3 but it's still loading the address instead

windozeuser · Oct 5, 2010

Fixed the problem, I used a pointer loaded by the X register,

HC11 convert BCD to binary

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