Rounding Algorithm Flowchart - Motorola M68060 User Manual

Floating-Point Unit
RN
GUARD AND LSB = 1,
ROUND AND STICKY = 0
GUARD = 1
ROUND OR STICKY = 1
ADD 1 TO
LSB
Result
Intermediate
Rounded-to-Nearest
handled in this manner. If the destination data format is extended and there is a difference
between the infinitely precise intermediate result and the round-to-nearest result, the rela-
–64
tive difference is 2
significant bit's value and is the worst case error that can be introduced when using the RN
6-14
RM
POS NEG POS
INTERMEDIATE
OR
RESULT
ADD 1 TO
LSB
OVERFLOW = 1
SHIFT MANTISSA
RIGHT 1 BIT,
ADD 1 TO EXPONENT
Figure 6-9. Rounding Algorithm Flowchart
Integer
x
x
(the value of the guard bit). This error is equal to one-half of the least
M68060 USER'S MANUAL
ENTRY
GUARD, ROUND,
AND STICKY BITS = 0
INEX2 1
SELECT ROUNDING MODE
RP RZ
NEG
INTERMEDIATE
RESULT
GUARD, ROUND,
AND STICKY ARE
CHOPPED
GUARD 0
ROUND 0
STICKY 0
EXIT
63-Bit Fraction Guard
xxx...x00
xxx...x00
EXACT RESULT
EXIT
Round Sticky
1 0 0
0 0 0
MOTOROLA