8051 Program - signed 16bit division

; subroutine DIV16

; 16-Bit / 16-Bit to 16-Bit Quotient & remainder signed Divide

; 2's Complement Format

;

; input: r1, r0 = Dividend X

; r3, r2 = Divisor Y

;

; output: r1, r0 = quotient Q of division Q = X / Y

; r3, r2 = remainder

; Carry C is set if Y = 0, i.e. divide by 0 attempted

;

; calls: UDIV16, Cr0r1, Cr2r3, Mr0r1

;

; alters: acc, r4, r5, r6, r7, flags, Bits 21H & 22H

DIV16:	anl PSW, #0E7H	;Register Bank 0
	mov a, r3	;get divisor high byte
	orl a, r2	;OR with low byte
	jnz div_OK	;divisor OK if not 0
	setb C	;else, overflow
	ret
div_OK:	push dpl
	push dph
	push b
	acall Cr0r1	;2's comp -> Mag/Sign
	acall Cr2r3	;2's comp -> Mag/Sign
	acall UDIV16
	acall Mr0r1	;Mag/Sign -> 2's Comp
	clr C
	pop b
	pop dph
	pop dpl
	ret	;done

Source: Maths Subroutines for the 8051 microcontroller, W.G.Marshall 2002

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Related topics:
8051 Program - signed 8bit division   |   8051 Program - unsigned 8bit division   |   8051 Program - unsigned 16bit division   |   8051 Program - signed 32bit division   |   8051 Program - unsigned 32bit division   |   8051 Program - memory subroutines   |   8051 Program - math subroutines   |   8051 Program - conversion subroutines

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