Floating Point Instructions
MOTOROLA
M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL
5-11
FADD
Floating-Point Add
FADD
(MC6888X, MC68040)
Operation:
Source + FPn
→
FPn
Assembler FADD. < fmt > < ea > ,FPn
Syntax: FADD.X FPm,FPn
*FrADD. < fmt > < ea > ,FPn
*FrADD.X FPm,FPn
where r is rounding precision, S or D
*Supported by MC68040 only.
Attributes: Format = (Byte, Word, Long, Single, Double, Extended, Packed)
Description: Converts the source operand to extended precision (if necessary) and adds
that number to the number contained in the destination floating-point data register.
Stores the result in the destination floating-point data register.
FADD will round the result to the precision selected in the floating-point control register.
FSADD and FDADD will round the result to single or double-precision, respectively,
regardless of the rounding precision selected in the floating-point control register.
Operation Table:
1. If either operand is a NAN, refer to 1.6.5 Not-A-Numbers for more information.
2. Returns + 0.0 in rounding modes RN, RZ, and RP; returns – 0.0 in RM.
3. Sets the OPERR bit in the floating-point status register exception byte.
DESTINATION
SOURCE
1
+ In Range – + Zero – + Infinity –
In Range +
–
Add
Add + inf – inf
Zero +
–
Add
+ 0.0 0.0
2
0.0
2
– 0.0
+ inf – inf
Infinity +
–
+ inf
– inf
+ inf
– inf
+ inf NAN
3
NAN
‡
– inf
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