Intel 80286, 80287 manual 207

NUMERIC PROGRAMMING EXAMPLES

iAPX286 MACRO ASSEMBLER	80287	Trillnometric Function5	10: 13: 51 091:25/83 PAGE
LOC OS,)	LINE	SOURCE
	,.

20

21

22

23

••

2.

.207

2a

••

30

31

3.

33

3.

35

30

37

38

3.

.0,

.2

.3

••

45 +1

.0

.7

.a

••

50

31

••

53

••

55

.0

07

5e

5.

00

01 ,

02

O.

03 :."

OS

00

07

08

o.

70 ,

71

7:1: +1 "Jllct

73

7. ,

75

This subroutine calculate. the 51ne OT' cosina of th. 4I"gle. giv.n in

Nldi.nll. Tha angle is in SHO), thll T'llturnod valu. will ba in STeO), Th. r •• ult h ju:c:u"at. to within 7 unUs of th. lI'i!IIst significant three

bitll of th. NPX utend&d ,.ul format. Tha PL.M/B6 d.flinition ill:

sina: prot_durl (angla) 1'1.1 axternall daclare angla '1' •• 11

and sin.,

COlina: procadu,.a <angl.) " ... 1 axternall dacla". angla ,. •• 11

end cOlinl1

Thrt'e ltack rellilterl are req,uir·ed. The result 0' thl! function is defined al follollls for thl' follollling arlluments:

	angle	relult
.... lid	unnormal leSI th.n 2**62 in magnitude	correc:t	.... lu •
zero		o or 1
denormal		correct	denormal
...al id or	unnormal greater than 2**62	ind.'inite
infinity		indeHnit:e
NAN		NAN
'mpty		Itmpty

Thi. fUnc:tion il b.ud on the NPX fptan instruction. The fptan

in.truction IUlll only lUork with an angle of from 0 to PI/4. With th:l.!i

.in.truction, the .ine or cOlinl" of! angl.1 f!rom 0 to Pl/4 can b. ar::curately

calculated. Th. ter::hniq.uI und by thh routine can r::alr::ulat. a gl"l1".l line or r::osine by uling on. of! four pO.libll op.ration.:

Lit R .. langle mod PI/41

S .. -1 1, ar::r::ording to thl sign of the .n)l1ll

2)co.eR)3) .inCPI/4-R) 4) COICPI/4-RI

Thl r::hoir::. of the relation and the sign of thl ruult follows the d.ci.ion tabl. Ihown belolll baud on the octant the angl. f.ll1 in:

octant	lint	c olinl
	.•••S*".	-1*1
	S*3	-1*4
	-9*1	-1*2
	-9*4	-1*3
	-6*2	1
	-9*3	•

Angle to lin. f!unction il a zero or unnormal.

OOOE

OOOE 0009

0010 7501

00l:ii! C3

70s i n'_1 Iro_unnormill:

78		fltp	It C1)	I RlmO"1	PI 14
7.		Jnz	entlr _I i nl_normal i z It	I Jump i,	angle is unno't'mal
eo
81		Angle il II nro.
e.		.. t
e3
8.	,	Angle	il an unnoT'mal.
eo
e.

0013

0013 E80901

0016 E9:i!F

OOlS

001S 09E5

COlA 9DDFEO

00 I D 2EDIJ2EOOOO

0022 BIOI

0024 9E

0025 7263

0027 D9C9 OO:ii!9 7Ale

87 'ntlr _.i nt_normal i z.:

e8
e.	c<lll	normalize_"alul
.0,	J.mp	Ihort Intlr_lin.
.••3	proc	..
COlin.
••	fits'"ham
••0	'Id	P i_q,uart.r
.7	mav	cl,l
.e	uhf
100••	J'	funnYJar.mltlr
101
10.	Angle	i . unnol"mal. normal,
103
10.	hch
10.	JP'	.nt,r_Iln"
100

J Entry point to r::olin'

Look at thl "alul

Star, Itatul ""41uI

ISltUP for angl. r,duel 6illnal COlin. funr::tion

ZF .. C3. PF .. C2, CF .. CO

I Jump 1f par.m.ter i .

I Imptl,!. NAN. or infinity

d.norm.l.

IstCO) .. angle. It'l) .. PI/4 I Jump if normal 01" d .normal

002D OD09

0020 75E4

107Angh i . .n unnormal

loa

10	htp	It( 1)	. 1.0
II.	Anlllt	i . . z.ro. cosCO)
110	Jnz	"nt r _, i n,,_normal i z eo
111

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

4-19