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Safe Division

Divides the value at register R0 by the value at register R1. The quotient is stored in R0 and the remainder in R1. The value of the B register remains unchanged.

; +-----------------------------------------------------------------+
; | subroutine: SAFE_DIV                                            |
; | 8-Bit / 8-Bit to 8-Bit Quotient & Remainder Unsigned Divide     |
; |                                                                 |
; | input:    R00 = Dividend X                                      |
; |           R01 = Divisor Y                                       |
; |                                                                 |
; | output:   R00 = quotient Q of division  ( Q = X / Y )           |
; |           R01 = remainder R of division ( R = X % Y )           |
; |                                                                 |
; | alters:   Carry Flag (C)                                        |
; |                                                                 |
; | notes:    If division by zero is attempted nothing happens      |
; |           and the Overflow Flag (OV) is not altered.            |
; +-----------------------------------------------------------------+

SAFE_DIV:       
JZ    
 
R01     
 
SADI_END
 
; Avoid division by zero
                
PUSH  
 
B       
 
; Save contents of B register
                
DIV   
 
R00     
 
R01     
                
MOV   
 
R01     
 
B       
                
POP   
 
B       
 
; Restore B register to previous value
SADI_END:       
RET