Subtract Unnormalized (Sur) (Su) (Swr) (Sw) - RCA 70/46 Reference Manual

Subtract
Unnormalized
(SUR) (SU) (SWR) (SW)
General Description
Format
(RR Short)
(RX
Short)
(RR Long)
(RX Long)
Condition Code
Interrupt Action
Notes
Floating-Point Instructions
• The operand specified by the second address (R
2
or XdB
2
/D
2 )
is sub-
tracted from the operand in the floating-point register specified by the first
address (R
1 ) .
The
unnormalized
difference is loaded into the register
specified by the first address. The sign and magnitude of the difference
determine the condition code.
o
7 8 11 12 15
o
7 8 11 12 15 16 19 20
o
7 8 11 12 15
o
7 8 11 12 15 16 19 20
• 0 - result mantissa is zero.
1 - result mantissa is less than zero.
2 - result mantissa is greater than zero.
3 - result exponent overflows.
• Address error:
Addressing (RX format).
Specification.
Significance error.
Exponent overflow.
31
31
• 1. Subtract Unnormalized differs from Subtract Normalized only in that
the difference is not normalized before it is loaded into the result
register.
2. Exponent underflow cannot occur.
214