Xerox 550 - Fss; Fsl; Condition Code Settings for Floating-Point Instructions

Table 8. Condition Code Settings for Floating-Point Instructions
Condition Code
1 2
3
4
Meaning If No Trap to Location X'44'
Meaning If Trap to Location X'44' Occurs
0
0
0 0 A x 0,
a/A, or -A + A(f) with FN= I )
*@
0
0
0 1
N
< 0
Normal
*
resu Its
0
0
1 0 N >0
*
0
1
0
0
*@
Divide by zero )
0 1 0 1
*
Overflow,
N < 0 Always trapped
0
1 1 0
*
Overflow,
N >0
0
0
0
-A +A
FS=O
@[:
-A + A(f) )
0
0
1
N
< 0 > 2 P t I FN = 0, and
N < 0)
rs= I FN=O
os norma -
>
2 Postnormal- d' d '
}
0 0 h0ft no underflow
. . . an no un er-
a.
1
0
N>O IZlngs IS
N >0
IZlng shifts flow with FZ= 1
1 1 0
0
Underflow with FZ=O and no trap by FS= 10
*
1
1
0
1
*
1 1
1 0
*
Notes:
(j)
Result set to "true" zero
@
"*,, indicates impossible configurations
®
Applies to add and subtract only where FN = 0
The R field of the FAL instruction must be an even value
for proper operation of the instruction; if the R field of FAl
is an odd value, the instruction traps to location X'4D',
instruction exception trap.
FSS
FLOATING SUBTRACT SHORT
rNord index alignment)
H 3ci R I X I: Referenc~ address I
0123145678 9 1011121314151617181912021222324252627128293031
The effective word and the contents of register R are loaded
into a set of internal registers.
FLOATING SUBTRACT SHORT forms the two's complement
of the effective word and then operates identically to
FLOATING ADD SH ORT (FAS), If no flo(lting-po!n
t
arithmetic fault occurs, the difference is loaded into reg-
ister R as a short-format floating-point number.
Affected: (R), CC
(R) - EW- R
Trap: Floating-point arith-
metic fault
78 Floating-Point Arithmetic Instructions
FSL
lC
o 1 2
Underflow,
N < a}
FZ= 1
Underflow,
N >0
FLOATING SUBTRACT LONG
(Doubleword index alignment)
I R I X II Reference
l
address I
718 10 11112 13 14 115116 17 18 1912021 22 23124 25 26 27128 29 30 31'
The effective doubleword and the contents of registers R
and Ru 1 are loaded into a set of internal registers.
FLOATING SUBTRACT LONG forms the two's comple-
ment of the effective doubleword and then operates iden-
tically to FLOATING ADD LONG (FAL). If no floating-
point arithmetic fault occurs, the difference is loaded into
registers Rand Ru 1 as a long-format floating-point number.
Affected: (R), (Ru 1), CC
(R, Rul) - ED -R, Ru1
Trap: Floating-point arith-
metic fault, instruc-
tion exception
The R field of the FSL instruction must be an even value for
proper operation of the instruction; if the R field of FSL is
an odd value, the instruction traps to location X'4D',
instruction exception trap.