User's Manual

iAPX286 MACRO ASSEMBLER
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NUMERIC PROGRAMMING EXAMPLES
80287 Trillnometric Function5
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II.
SOURCE
,
:."
,
"Jllct
,
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
.... lid unnormal leSI th.n 2**62 in magnitude
zero
denormal
... al id or unnormal greater than 2**62
infinity
NAN
'mpty
relult
correc:t .... lu •
o or 1
correct denormal
ind.'inite
indeHnit:e
NAN
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.
s i n'_1 Iro_unnormill:
,
fltp
Jnz
It C 1)
entlr _I i nl_normal i z It
Angle il II nro.
.. t
Angle il an unnoT'mal.
'ntlr _.i nt_normal i z.:
c<lll
normalize_"alul
J.mp Ihort Intlr_lin.
COlin.
proc
ham
fits'"
..
'Id
P i_q,uart.r
mav cl,l
uhf
J'
funnYJar.mltlr
Angle
i.
unnol"mal.
normal,
hch
JP'
.nt,r_Iln"
Angh
i. .n unnormal
htp
It( 1)
Jnz "nt.r _, i n,,_normal i z eo
Anlllt i. . z.ro. cosCO)
.
1.0
I RlmO"1 PI 14
I Jump i, angle is unno't'mal
J Entry point to r::olin'
Look at thl "alul
Star, Itatul ""41uI
I SltUP 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.
I stCO) .. angle. It'l) .. PI/4
I Jump if normal 01" d .normal
Figure 4-7. Calculating Trigonometric Functions (Cont'd.)
4-19