Control Data Cyber 170 State Hardware Reference Manual page 135

CP
Mask
Instruction
CP Mask lnstruction
Form Mask
Form mask of jk b i t s t o X i
This i n s t r u c t i o n g e n e r a t e s a masking word u s i n g t h e j and
k
d e s i g n a t o r s a s
parameters.
N o operands a r e read from o p e r a t i n g r e g i s t e r s . 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 a s a s i n g l e , 6-bit o c t a l q u a n t i t y t o d e s i g n a t e t h e
width of t h e masking f i e l d . A f i e l d of l ' s , beginning a t t h e highest-order end
of t h e word, i s extended downward on a background of 0 ' s . The completed
masking word c o n s i s t s of 1 b i t s i n t h e highest-order jk b i t p o s i t i o n s and 0
b i t s i n t h e remainder of t h e word. This masking word i s t h e n d e l i v e r e d t o X i .
The following a r e sample parameters.
This i n s t r u c t i o n g e n e r a t e s v a r i a b l e width masks f o r l o g i c a l o p e r a t i o n s . T h i s
i n s t r u c t i o n , t o g e t h e r with a s h i f t i n s t r u c t i o n , g e n e r a l l y c r e a t e s an a r b i t r a r y
f i e l d mask f a s t e r t h a n reading a pregenerated mask from CM.