User's Manual

iAPX286 MACRO ASSEMBLER
LOC DB..}
0012
0012 EBOODO
0015 81308
0017 2EBAB70200
ODIC 3CFE
ODIE 7528
0020 C20AOO
0023
0023 ODDS
0025 EB02
0027
0027 BOFE
0029
0029 C9
002A 07
00213 C20AOO
002E
002E DI37EFO
0031 A801
0033 98
0034 74F3
0086 DBDoeo
0039 285EF6
003C OBSEF4
003F OB5EF2
0042 OB5EFO
0045 75E2
0047 B003
0049 EBDE
0048
0048 06
004C eS100aoo
0050 884EOB
0053 B3F902
0056 7CCF
0058 49
0059 83F912
Dose 7603
DOSE B91200
OD61
0061 3C06
0063 ?DBE
0065 3C04
0067 7DCS
0069 D9El
006B 8800
0060 33CO
006F 8B7EOE
0072 8905
0074 BB5E06
0077 8907
0079 eOFAFC
007C 7828
D07E SOFAFA
0081 732C
NUMERIC PROGRAMMING EXAMPLES
80287 Floating-Point to 18-Dig.it ASCII Conversion 10: 12: 38 09/25/83 PAGE
LINE
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SOURCE
call
tos_status
b 1, ax
a1,status_table[bx]
OIL INVALID
Look at status of ST(O)
Get descriptor frOm table
Look for empty STeO)
ST(O) is empty! Return the status value.
RE'move
infinity from stack and exit.
fstp
Jm,
st (0)
short exit_proc
; OK to leave fstp running
String space is too small! Return invalld code
OIL INVALID
leave
i RestorE.' stack
pop es
ret parms_size
ST(O) is NAN or indefinite. Store the value in memory and look
at the fraction field to separate indefinite from an ordinary NAN.
fstp fraction
test ai, MINUS
fwait
JZ exit.JIroc
mov bx.OCOOOH
sub bx.word ptr fraction+6
bx. word ptr fraction+4
bx. word ptr fraction+2
or bx. word ptr fraction
Jnz 9xit..JH·OC
al, INDEFINITE
Jmp exit.JIroc
Remove value from stack for examination
Look at sign bit
Insure stoT'e is done
Can't be indefinite if positive
Match against upper 16 bits· of fraction
CompaT'e bits 63-48
Bits 32-47 must be zero
Bits,l'31-16 must be zero
Bits 15-0 must be zero
Set return value for indefinite value
Allocate stack space for local variables and establish parameter
addressibility.
not_empty:
size_ok:
push
"
enter 10cal_size.O
mov
cx. field_size
<m,
cx.2
Jl
small_string
do<
"
<m,
c x. BCD_DIGITS
J"
size_ok
c x. BCD_DIGITS
<m, aI. INFINITY
".
found_i nfi n i ty
<m, al. NAN
JO'
NAN_or _indefinite
Save working register
FOT'mat stOiC II
Check for enough string space
AdJust for sign character
See if string is too large for BCD
Else set maximum string size
Look for infinity
Return status value for + or - inf,
Look for NAN or INDEFINITE
Set default return values and check that the number is normalized.
mov
mov
<m,
J.'
<m,
J ••
dx. ax
ax. ax
di. denormal.JItr
word ptr [di.:J, ax
bx. power .JItr
word ptr [bx]. ax
dl. ZERO
real_zero
dl. DENORMAL
found_denormal
Use positive value onll,l
sign bit in 011 has true sign of value
Save retuT'n value for later
Form a constant
Zero denormal count
Zero power of ten value
Test for zero
Skip power code if value is
Look for a denormal value
Handle it specially
Figure 4-6. Floating-Point to ASCII Conversion Routine (Cont'd.)
4-9