Intel 80286, 80287 manual 0o,3

NUMERIC PROGRAMMING EXAMPLES

i AP X:286 MACRO ASSEMBLER

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B0287 T1'ignometl'ic Functioni; 10: 13: 51 09/25/83 PAGE

LINE SOURCE

207

20B , Assert:: 0 ( steOl <- PII4

20.

210dD_sine_fphn:

212	flpten		,	TAN 9nO) • STeu/snol ... V/X
213	IIfte" _sine_flpten:
.14
210	te . t	bh.highCmilsk	c:and3 + m.sk cond!).	L.ao. at octant angle fell into
21.
.17.	JPo	X_numeT'atoT'	I	C.lcul.te cosine 'aT' Dctenh
21B			I 1,2.9.6

220Calculate the sine of the aT'~ument.

221sinCA) ... tanCA)/sq,T't<1+tanCA)**2)if tenCA) ... V/X then

2 ••sinCA) ... V/sqrt(X_X + V-V)

22'

224		'Id	stCl)	I	Cop V V value
22'		Jmp	shoT't finhh_sine	I	Put V value in numeT'atoT'
22.	,	The top 0' the stack is eUheT'		NAN. infinitv. OT' emptv .
• 27
22B
229	funnv"paT'ameteT':
230		fstp	steO)	,	Remove PII4
231
=		J'	retuT'n_empt"	I	Return empt\l if no paT'm
233		JPO	T'.tuT'n..NAN		Jump if st(OI is NAN
.34				I
235		st(O)	is infinit". R.tuT'n· an	indefinite	value.
23.
237		'pT'em			STell can be ·.n\lthing
2.B				I
23.

240T'etuT'n..NAN:

.41	T'etuT'n_emp tV:
.42				Ok to hillve fpT'em T'unning
243		•• t	I
244		Simuleh 'ptan lIIith ~tCO)	... 0
245	I
2 ••	,
.47	Il.ne_aT'gument_zeT'o:
.4B				Simulate tanCO)
•••2.0			I
			I	RetuT'n the zeT'O value
201		The anllh ilia. tao laT'lIe.	Remove the modulull and divl.dend fT'om the
2.2

253stack and retuT'n an indefinite T'e~ult.

2••

••5

2••

257		fcompp				I	Pop tlllO valulls for'om the stack
25B		Hd	indefinite			I	RetuT'n indefinite
•••2.0		rot					Wait foT' load to finish
		flllOl1t				I
•• 1		Calculate the cosine of the aT'gument.
2 ••
2.3		cosCA)	- 1/sqrtC1+tanCA)**2)		if	tenIA)	III V/X	then
2.'	,	cas (A)	= X/sq,rtex*x +	V*V)
••5
2 ••	X_numeT'atoT':					,
2.7			st(O)				COP\!	X value
2.B		fld
2 ••		fxch	~t(2)				Put X in		numeT'atoT'
270	finish _sine:
271						,
272		fmul	st. st(O)				FOT'm	x*x	+ V.V
27.
274		Fxch	st,st(O)
27S		fmul						=
.7.		hdd					st<O)		X'X + V*V
277		hq,rt					steOI	. sqrteX*X + V*V)
278
27.		FOT'm	the sign of the T'esult.		The	hID conditions			are the Cl flag 'T'tlm
2BO
2Bl		FXAM in bh and the CO flag fT'om IpT'em in ah.
28.			bh, high (mask	condO)			Look at the fprem CO flag
28.		and
2B4		.nd	ah, highemask	condl)			Look at the ham Cl flag
B5		D.	bh, ah				Even numbeT' of flags cancel
.8.		JPe	positive_sine				TIllO negatives m.ake a positive
2B7		fchs					FOT'ce	T'esult negative
.88
2B.
2'0
2.1		fdiv					Form	final result
2.2
2.3		rot					Ok to leave fdiv running
2.4
2.'	casine endp
296 +1	'eJect
2.7		This function !IIill calculate the tangent of an angle.
2.B
2.'		The angle, in T'adians is pa.sed in ST(O), the tangent is T'eturned

300in ST(OL The tangent is calculated to OIn aCCUT'aCU of 4 units in the

Figure 4-7. Calculating Trigonometric Functions (Cont'd.)

4-21