Control Data Cyber 170 State Hardware Reference Manual page 92

CP Shift Instructions
Right Shift
2 l i j k Right s h i f t (Xi) by jk
This i n s t r u c t i o n r e a d s one operand from X i , s h i f t s the 60-bit word r i g h t with
s i g n extension by jk b i t p o s i t i o n s , and w r i t e s t h e r e s u l t i n g 60-bit word back
i n t o t h e same X i r e g i s t e r . The j and k d e s i g n a t o r s a r e t r e a t e d as a s i n g l e
6-bit p o s i t i v e i n t e g e r operand i n t h i s i n s t r u c t i o n .
A
r i g h t s h i f t with s i g n extension implies t h a t t h e b i t p a t t e r n i n the 60-bit
word i s displaced toward t h e lowest-order b i t p o s i t i o n s .
The b i t s s h i f t e d o f f
the lower end of t h e word a r e discarded. The highest-order b i t p o s i t i o n s a r e
f i l l e d wtth copies of t h e o r i g i n a l s i g n b i t .
Two
sample computations a r e l i s t e d i n o c t a l n o t a t i o n t o i l l u s t r a t e the
operation performed.
An example of a p o s i t i v e operand i s a s follows:
I n i t i a l (Xi) 2004 7655 0002 3400 0004
Final (Xi) 0000 0000 2004 7655 0002
An example of a negative operand i s a s follows:
I n i t i a l (Xi) = 6000 4420 2222 0000 5643
jk
=
10 ( o c t a l )
F i n a l (Xi) = 7774 0 0 U 0404 4440 0013
This i n s t r u c t i o n , t o g e t h e r with i n s t r u c t i o n 20, may be used whenever a d a t a
word i s t o be s h i f t e d by a predetermined amount. I f the amount of s h i f t i s
derived i n t h e execution of t h e program, use i n s t r u c t i o n 22 o r 23.