$title	(extended math routine)

$mod51

$nolist

$nosymbols

$include(z80.inc)

$include(mymon.inc)

$include(controls.inc)

$list

temp	data	22h

Z	equ	0D5h		; zero flag

M	equ	0e7h		; negative flag



if(school=1)

	org	7800h

else

	org	0f800h

endif

eadd:	ljmp	exadd

esub:	ljmp	exsub

emul:	ljmp	exmul

ediv:	ljmp	exdiv

;=============================================================================



; HL = HL + DE

EXADD:	mov	a,Hreg

	xrl	a,Dreg

	anl	a,#80h		; clear sign

	dadd

	jnz	esign

	rrc	a	

	xrl	a,Hreg

	rlc	a

	jnc	esign

	call	overflow



;set sign and zero flags to reflect HL

esign:	clr	c

	clr	a

	add	a,Hreg

	jz	esgn1

	ret

esgn1:	add	a,Lreg

	jnz	esgn2

	ret

esgn2:	clr	a

	clr	c

	inc	a

	ret

;=============================================================================

; HL = HL - DE

EXSUB:	pushde

	xchg

	NEGHL

	call	exadd	

	popde

	ret

;=============================================================================

; HL = HL * DE

EXMUL:	pushbc

	pushde

	call	rsltsign	; b = sign of result

	mov	a,Hreg		; get hi byte

	jz	hlsmall		; if 8 bit ok

	mov	a,Dreg		; get hi byte

	jz	exm1		; if 8 bit ok

	call	overflow

exm1:	xchg

hlsmall:

	mov	a,Lreg		; get multiplier

	mov	Lreg,#0		; clear result

	mov	Hreg,#0

xmloop:

	clr	c

	rrc	a



	push	acc

	push	psw

	clr	a

	rrc	a

	add	a,#30h

	lcall	sndchr

	pop	psw

	pop	acc



	jnc	shiftop		; if no carry * 2

	dadd			; * 1

	jnc	shiftop

	lcall	overflow

shiftop:

	xchg

	dadh

	jnc	emx2

	lcall	overflow

emx2:	xchg

	jnz	xmloop

	popde

	

signrcl:

	mov	a,Hreg

	rlc	a

	jnc	srcl1

	call	overflow



srcl1:	mov	a,Breg

	rlc	a		; get result sign

	jnc	srcl2

	NEGHL

srcl2:	popbc

	jmp	esign

;=============================================================================

; HL = HL / DE

EXDIV:	pushbc			; save BC pair

	clr	a

	clr	c

	orl	a,Ereg

	orl	a,Dreg

	jnz	ed1

	call	overflow

ed1:	call	rsltsign

	mov	a,Hreg

	orl	a,Dreg

	rlc	a

	jnc	ed2

	call	overflow

ed2:	pushbc

	mov	a,Ereg

	mov	Creg,a

	mov	a,Dreg

	mov	Breg,a

	mov	Dreg,#0

	mov	Ereg,#0

	pushde

	xchg

	mov	Hreg,#0

	mov	Lreg,#1

dbldiv:	dadh

	xchg

	dadh	

	call	cmpbh

	xchg

	jnc	dbldiv

	xchg

hafdiv:	xchg

	call	divby2

	jb	Z,divdun

	xchg

	call	divby2

	call	cmpbh

	jb	M,hafdiv

	clr	c

	mov	a,Creg

	subb	a,Lreg

	mov	Creg,a

	mov	a,Breg

	subb	a,Hreg

	mov	Breg,a

	XTHL

	DADD

	XTHL

	sjmp	hafdiv

divdun:	pophl

	mov	a,Creg

	mov	Ereg,a		; remainder

	mov	a,Breg

	mov	Dreg,a

	popbc

	jmp	signrcl		



; compute sign of result for exmul and exdiv	

RSLTSIGN:

	mov	a,Hreg

	mov	Breg,a

	rlc	a		; shift sign to carry

	jnc	rslt1		; is positive

	NEGHL			; 2's compliment

rslt1: 	xchg

	mov	a,Hreg

	xrl	a,Breg		; xor both sign bits

	mov	Breg,a		; save

	mov	a,Hreg

	rlc	a

	jnc	rs2		

	NEGHL

rs2:	ret



CMPBH:	CLR	C

	MOV	a,Creg

	SUBB	a,Lreg

	mov	a,Breg

	subb	a,Hreg

	ret



; divide HL pair by 2 (CHECKED)

divby2:	clr	C

	mov	a,Hreg

	rrc	a

	mov	Hreg,a

	mov	a,Lreg

	rrc	a

	mov	Lreg,a

	orl	a,Hreg

	clr	Z

	jnz	db2

	setb	Z

db2:	ret

;

overflow:

	lcall	ilprt

	db	cr,lf,7,'Overflow @',0

	xthl

	mov	dph,r7

	mov	dpl,r6

	xthl

	lcall	prtaddr

	lcall	ilprt

	db	'HL: ',0

	mov	dph,r7

	mov	dpl,r6

	lcall	prtaddr

	mov	a,#' '

	lcall	sndchr

	lcall	ilprt

	db	'DE: ',0

	mov	dpl,4

	mov	dph,5

	lcall	prtaddr

	lcall	crlf

	setb	ov

	pop	acc

	pop	acc

	ljmp	warm

lastcode	equ	$



	end